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| CMOS DUAL SyncFIFOTM DUAL 256 x 18, DUAL 512 x 18, DUAL 1,024 x 18, DUAL 2,048 x 18 and DUAL 4,096 x 18 IDT72805LB IDT72815LB IDT72825LB IDT72835LB IDT72845LB FEATURES: * * * * * * * * * The IDT72805LB is equivalent to two IDT72205LB 256 x 18 FIFOs The IDT72815LB is equivalent to two IDT72215LB 512 x 18 FIFOs The IDT72825LB is equivalent to two IDT72225LB 1,024 x 18 FIFOs The IDT72835LB is equivalent to two IDT72235LB 2,048 x 18 FIFOs The IDT72845LB is equivalent to two IDT72245LB 4,096 x 18 FIFOs Offers optimal combination of large capacity (8K), high speed, design flexibility, and small footprint Ideal for the following applications: - Network switching - Two level prioritization of parallel data - Bidirectional data transfer - Bus-matching between 18-bit and 36-bit data paths - Width expansion to 36-bit per package - Depth expansion to 8,192 words per package 10ns read/write cycle time, 6.5ns access time IDT Standard or First Word Fall Through timing * * * * * * * * * Single or double register-buffered Empty and Full Flags Easily expandable in depth and width Asynchronous or coincident Read and Write clocks Asynchronous or synchronous programmable Almost-Empty and Almost-Full flags with default settings Half-Full flag capability Output Enable puts output data bus in high-impedance state High-performance submicron CMOS technology Available in the 128-pin Thin Quad Flatpack (TQFP). Also available for the IDT72805LB/72815LB/72825LB, in the 121-lead, 16 x 16 mm plastic Ball Grid Array (PBGA) Industrial temperature range (-40C to +85C) is available DESCRIPTION: The IDT72805LB/72815LB/72825LB/72835LB/72845LB are dual 18-bit-wide synchronous (clocked) First-in, First-out (FIFO) memories. One dual IDT72805LB/ 72815LB/72825LB/72835LB/72845LB device is functionally equivalent to two FUNCTIONAL BLOCK DIAGRAM FFA/IRA WCLKA WENA HFA/(WXOA) PAEA EFA/ ORA WCLKB WENB PAFA DA0-DA17 LDA DB0-DB17 LDB INPUT REGISTER OFFSET REGISTER INPUT REGISTER OFFSET REGISTER FFB/IRB PAFB EFB/ORB PAEB HFB/(WXOB) WRITE CONTROL LOGIC WRITE POINTER FLA WXIA (HFA)/WXOA RXIA RXOA RSA RAM ARRAY 256 x 18 512 x 18 1,024 x 18 2,048 x 18 4,096 x 18 FLAG LOGIC WRITE CONTROL LOGIC READ POINTER READ CONTROL LOGIC WRITE POINTER RAM ARRAY 256 x 18 512 x 18 1,024 x 18 2,048 x 18 4,096 x 18 FLAG LOGIC READ POINTER READ CONTROL LOGIC EXPANSION LOGIC OUTPUT REGISTER EXPANSION LOGIC OUTPUT REGISTER RESET LOGIC RESET LOGIC OEA QA0-QA17 RCLKA RENA RSB RXOB RXIB (HFB)/WXOB WXIB FLB OEB QB0-QB17 RCLKB RENB 3139 drw 01 IDT and the IDT logo are registered trademarks. The SyncFIFO is a trademark of Integrated Device Technology, Inc. COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES 1 2003 Integrated Device Technology, Inc. All rights reserved. Product specifications subject to change without notice. FEBRUARY 2003 DSC-3139/4 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES DESCRIPTION (Continued) IDT72205LB/72215LB/72225LB/72235LB/72245LB FIFOs in a single package with all associated control, data, and flag lines assigned to independent pins. These devices are very high-speed, low-power First-In, First-Out (FIFO) memories with clocked read and write controls. These FIFOs are applicable for a wide variety of data buffering needs, such as optical disk controllers, Local Area Networks (LANs), and interprocessor communication. Each of the two FIFOs contained in these devices has an 18-bit input and output port. Each input port is controlled by a free-running clock (WCLK), and an input enable pin (WEN). Data is read into the synchronous FIFO on every clock when WEN is asserted. The output port of each FIFO bank is controlled by another clock pin (RCLK) and another enable pin (REN). The Read Clock can be tied to the Write Clock for single clock operation or the two clocks can run asynchronous of one another for dual-clock operation. An Output Enable pin (OE) is provided on the read port of each FIFO for three-state control of the output. The synchronous FIFOs have two fixed flags, Empty Flag/Output Ready (EF/OR) and Full Flag/Input Ready (FF/IR), and two programmable flags, Almost-Empty (PAE) and Almost-Full (PAF). The offset loading of the program- mable flags is controlled by a simple state machine, and is initiated by asserting the Load pin (LD). A Half-Full flag (HF) is available for each FIFO that is implemented as a single device configuration. There are two possible timing modes of operation with these devices: IDT Standard mode and First Word Fall Through (FWFT) mode. In IDT Standard Mode, the first word written to an empty FIFO will not appear on the data output lines unless a specific read operation is performed. A read operation, which consists of activating REN and enabling a rising RCLK edge, will shift the word from internal memory to the data output lines. In FWFT mode, the first word written to an empty FIFO is clocked directly to the data output lines after three transitions of the RCLK signal. A REN does not have to be asserted for accessing the first word. These devices are depth expandable using a daisy-chain technique or First Word Fall Through (FWFT) mode. The XI and XO pins are used to expand the FIFOs. In depth expansion configuration, FL is grounded on the first device and set to HIGH for all other devices in the Daisy Chain. The IDT72805LB/72815LB/72825LB/72835LB/72845LB are fabricated using IDT's high-speed submicron CMOS technology. PIN CONFIGURATIONS PIN 1 A WCLKA DA3 DA1 DA0 DB13 DB16 RCLKB LDB RSB QB17 QB16 B PAFA DA4 WENA DA2 DB12 DB15 RENB OEB EFB QB15 QB14 C FFA RXIA WXIA DA5 DB14 DB11 GND DB17 GND QB13 QB11 D RXOA QA0 QA2 FLA DB8 DB10 DB7 VCC QB12 QB10 QB8 E QA1 QA4 QA3 WXOA/ HFA PAEA DB9 DB6 VCC VCC QB9 QB7 F QA5 QA6 GND VCC GND GND GND VCC GND QB6 QB5 G QA7 QA9 VCC VCC DA6 DA9 PAEB WXOB/ HFB QB3 QB4 QB1 H QA8 QA10 QA12 VCC DA7 DA10 DA8 FLB QB2 QB0 RXOB J QA11 QA13 GND DA17 GND DA11 DA14 DB5 WXIB RXIB FFB K QA14 QA15 EFA OEA RENA DA15 DA12 DB2 WENB DB4 PAFB L QA16 QA17 RSA LDA RCKLA DA16 DA13 DB0 DB1 DB3 WCLKB 1 2 3 4 5 6 7 8 9 10 11 3139 drw 02 NOTE: 1. The PBGA is only available for the IDT72805LB/72815LB/72825LB in the 15 or 25 ns speed grade. PBGA (BG121-1, order code: BG) TOP VIEW 2 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES PIN CONFIGURATIONS (Continued) INDEX 128 127 126 125 124 123 122 121 120 119 118 117 116 115 114 113 112 111 110 109 108 107 106 105 104 103 WXIA WENA WCLKA FLA PAEA DA0 DA1 DA2 DA3 DA4 DA5 DA6 DA7 DA8 DA9 DA10 DA11 DA12 DA13 DA14 DA15 DA16 DA17 GND RCLKA RENA QB0 QB1 GND QB2 QB3 VCC QB4 GND QB5 QB6 QB7 QB8 GND QB9 QB10 VCC QB11 QB12 GND QB13 QB14 VCC QB15 GND QB16 QB17 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 VCC PAFA RXIA FFA WXOA/HFA RXOA QA0 QA1 GND QA2 QA3 VCC QA4 GND QA5 QA6 QA7 QA8 GND DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 PAEB FLB WCLKB WENB WXIB VCC PAFB RXIB FFB WXOB/HFB RXOB 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 LDA OEA RSA VCC GND EFA QA17 QA16 GND QA15 VCC QA14 QA13 GND QA12 QA11 VCC QA10 QA9 DB8 DB9 DB10 DB11 DB12 DB13 DB14 DB15 DB16 DB17 GND RCLKB RENB LDB OEB RSB VCC GND EFB 3139 drw 02a TQFP (PK128-1, order code: PF) TOP VIEW 3 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES PIN DESCRIPTION Symbol DA0-DA17 DB0-DB17 RSA RSB WCLKA WCLKB WENA WENB RCLKA RCLKB RENA RENB OEA OEB LDA LDB FLA FLB Name Data Inputs Reset Write Clock Write Enable Read Clock Read Enable Output Enable Load I/O I I I I I I I I Data inputs for an 18-bit bus. When RS is set LOW, internal read and write pointers are set to the first location of the RAM array, FF and PAF go HIGH, and PAE and EF go LOW. A reset is required before an initial WRITE after power-up. When WEN is LOW, data is written into the FIFO on a LOW-to-HIGH transition of WCLK, if the FIFO is not full. When WEN is LOW, data is written into the FIFO on every LOW-to-HIGH transition of WCLK. When WEN is HIGH, the FIFO holds the previous data. Data will not be written into the FIFO if the FF is LOW. When REN is LOW, data is read from the FIFO on a LOW-to-HIGH transition of RCLK, if the FIFO is not empty. When REN is LOW, data is read from the FIFO on every LOW-to-HIGH transition of RCLK. When REN is HIGH, the output register holds the previous data. Data will not be read from the FIFO if the EF is LOW. When OE is LOW, the data output bus is active. If OE is HIGH, the output data bus will be in a high-impedance state. When LD is LOW, data on the inputs D0-D11 is written to the offset and depth registers on the LOW-to-HIGH transition of the WCLK, when WEN is LOW. When LD is LOW, data on the outputs Q0-Q11 is read from the offset and depth registers on the LOW-to-HIGH transition of the RCLK, when REN is LOW. In the single device or width expansion configuration, FL together with WXI and RXI determine if the mode is IDT Standard mode or First Word Fall Through (FWFT) mode, as well as whether the PAE/PAF flags are synchronous or asynchronous. (See Table I.) In the Daisy Chain Depth Expansion configuration, FL is grounded on the first device (first load device) and set to HIGH for all other devices in the Daisy Chain. In the single device or width expansion configuration, WXI together with FL and RXI determine if the mode is IDT Standard mode or FWFT mode, as well as whether the PAE/PAF flags are synchronous or asynchronous. (See Table 1.) In the Daisy Chain Depth Expansion configuration, WXI is connected to WXO (Write Expansion Out) of the previous device. In the single device or width expansion configuration, RXI together with FL and WXI, determine if the mode is IDT Standard mode or FWFT mode, as well as whether the PAE/PAF flags are synchronous or asynchronous. (See Table 1.) In the Daisy Chain Depth Expansion configuration, RXI is connected to RXO (Read Expansion Out) of the previous device. In the IDT Standard mode, the FF function is selected FF indicates whether or not the FIFO memory is full. In the FWFT mode, the IR function is selected. IR indicates whether or not there is space available for writing to the FIFO memory. In the IDT Standard mode, the EF function is selected. EF indicates whether or not the FIFO memory is empty. In FWFT mode, the OR function is selected. OR indicates whether or not there is valid data available at the outputs. When PAE is LOW, the FIFO is almost-empty based on the offset programmed into the FIFO. The default offset at reset is 31 from empty for IDT72805LB, 63 from empty for IDT72815LB, and 127 from empty for IDT72825LB/72835LB/72845LB. When PAF is LOW, the FIFO is almost-full based on the offset programmed into the FIFO. The default offset at reset is 31 from full for IDT72805LB, 63 from full for IDT72815LB, and 127 from full for IDT72825LB/72835LB/ 72845LB. In the single device or width expansion configuration, the device is more than half full when HF is LOW. In the depth expansion configuration, a pulse is sent from WXO to WXI of the next device when the last location in the FIFO is written. In the depth expansion configuration, a pulse is sent from RXO to RXI of the next device when the last location in the FIFO is read. Data outputs for an 18-bit bus. +5V power supply pins. Ground pins. Description First Load I WXIA WXIB Write Expansion Input I RXIA RXIB Read Expansion Input I FFA/IRA FFB/IRB EFA/ORA EFB/ORB PAEA PAEB PAFA PAFB WXOA/HFA WXOB/HFB RXOA RXOB QA0-QA17 QB0-QB17 VCC GND Full Flag/ Input Ready Empty Flag/ Output Ready Programmable Almost-Empty flag Programmable Almost-Full flag Write Expansion Out/Half-Full Flag Read Expansion Out Data Outputs Power Ground O O O O O O O 4 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES ABSOLUTE MAXIMUM RATINGS Symbol VTERM TSTG IOUT Rating Terminal Voltage with respect to GND Storage Temperature DC Output Current Commercial -0.5 to +7.0 -55 to +125 -50 to +50 Unit V RECOMMENDED DC OPERATING CONDITIONS Symbol VCC GND VIH VIL(1) TA TA Parameter Supply Voltage (Com'l/Ind'l) Supply Voltage (Com'l/Ind'l) Input High Voltage (Com'l/Ind'l) Input Low Voltage (Com'l/Ind'l) Operating Temperature Commercial Operating Temperature Industrial Min. 4.5 0 2.0 0 0 Typ. 5.0 0 Max. 5.5 0 0.8 70 85 Unit V V V V C C C mA NOTE: 1. Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. NOTE: 1. 1.5V undershoots are allowed for 10ns once per cycle. DC ELECTRICAL CHARACTERISTICS (Commercial: VCC = 5V 10%, TA = 0C to +70C; Industrial: VCC = 5V 10%, TA = -40C to +85C) IDT72805LB IDT72815LB IDT72825LB IDT72835LB IDT72845LB Com'l & Ind'l(1) tCLK = 10, 15, 25 ns Typ. -- -- -- -- -- -- Symbol ILI (2) Parameter Input Leakage Current (any input) Output Leakage Current Output Logic "1" Voltage, IOH = -2 mA Output Logic "0" Voltage, IOL = 8 mA Active Power Supply Current Standby Current Min. -1 -10 2.4 -- -- -- Max. 1 10 -- 0.4 100 10 Unit A A V V mA mA ILO(3) VOH VOL ICC1 (4,5,6) ICC2(4,7) NOTES: 1. 2. 3. 4. 4. 5. Industrial Temperature Range Product for the 15ns speed grade is available as a standard device. Measurements with 0.4 VIN VCC. OE VIH, 0.4 VOUT VCC. Tested with outputs open (IOUT = 0). RCLK and WCLK toggle at 20 MHZ and data inputs switch at 10 MHz. For the IDT72805LB/72815LB/72825LB the typical ICC1 = 2[1.81 + 1.12*fS + 0.02*CL*fS] (in mA); for the IDT72835LB/72845LB the typical ICC1 = 2[2.85 + 1.30*fS + 0.02*CL*fS] (in mA). These equations are valid under the following conditions: VCC = 5V, TA = 25C, fS = WCLK frequency = RCLK frequency (in MHz, using TTL levels), data switching at fS/2, CL = capacitive load (in pF). 7. All Inputs = VCC - 0.2V or GND + 0.2V, except RCLK and WCLK, which toggle at 20 MHz. CAPACITANCE (TA = +25C, f = 1.0MHz) Symbol CIN (2) Parameter(1) Input Capacitance Output Capacitance Conditions VIN = 0V VOUT = 0V Max. 10 10 Unit pF pF COUT(1,2) NOTES: 1. With output deselected, (OE VIH). 2. Characterized values, not currently tested. 5 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES AC ELECTRICAL CHARACTERISTICS (Commercial: VCC = 5V 10%, TA = 0C to +70C; Industrial: VCC = 5V 10%, TA = -40C + 85C) Commercial IDT72805LB10 IDT72815LB10 IDT72825LB10 IDT72835LB10 IDT72845LB10 Symbol fS tA tCLK tCLKH tCLKL tDS tDH tENS tENH tRS tRSS tRSR tRSF tOLZ tOE tOHZ tWFF tREF tPAFA tPAFS tPAEA tPAES tHF tXO tXI tXIS tSKEW1 tSKEW2(4) Parameter Clock Cycle Frequency Data Access Time Clock Cycle Time Clock HIGH Time Clock LOW Time Data Setup Time Data Hold Time Enable Setup Time Enable Hold Time Reset Pulse Width(2) Reset Setup Time Reset Recovery Time Reset to Flag and Output Time Output Enable to Output in Low-Z(3) Output Enable to Output Valid Output Enable to Output in High-Z(3) Write Clock to Full Flag Read Clock to Empty Flag Clock to Asynchronous Programmable Almost-Full Flag Write Clock to Synchronous Programmable Almost-Full Flag Clock to Asynchronous Programmable Almost-Empty Flag Read Clock to Synchronous Programmable Almost-Empty Flag Clock to Half-Full flag Clock to Expansion Out Expansion In Pulse Width Expansion In Setup Time Skew time between Read Clock & Write Clock for FF/IR and EF/OR Skew time between Read Clock & Write Clock for PAE and PAF Min. -- 2 10 4.5 4.5 3 0 3 0 10 8 8 -- 0 -- 1 -- -- -- -- -- -- -- -- 3 3 5 12 Max. 100 6.5 -- -- -- -- -- -- -- -- -- -- 15 -- 6 6 6.5 6.5 17 8 17 8 17 6.5 -- -- -- -- Com'l & Ind'l(1) IDT72805LB15 IDT72815LB15 IDT72825LB15 IDT72835LB15 IDT72845LB15 Min. -- 2 15 6 6 4 1 4 1 15 10 10 -- 0 -- 1 -- -- -- -- -- -- -- -- 6.5 5 6 15 Max. 66.7 10 -- -- -- -- -- -- -- -- -- -- 15 -- 8 8 10 10 20 10 20 10 20 10 -- -- -- -- Commercial IDT72805LB25 IDT72815LB25 IDT72825LB25 IDT72835LB25 IDT72845LB25 Min. -- 3 25 10 10 6 1 6 1 25 15 15 -- 0 -- 1 -- -- -- -- -- -- -- -- 10 10 10 17 Max. 40 15 -- -- -- -- -- -- -- -- -- -- 25 -- 12 12 15 15 35 12 35 12 35 15 -- -- -- -- Unit MHz ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns NOTES: 1. Industrial Temperature Range Product for the 15ns speed grade is available as a standard device. 2. Pulse widths less than minimum values are not allowed. 3. Values guaranteed by design, not currently tested. 4. tSKEW2 applies to synchronous PAE and synchronous PAF only. 5V 1.1K AC TEST CONDITIONS Input Pulse Levels Input Rise/Fall Times Input Timing Reference Levels Output Reference Levels Output Load GND to 3.0V 3ns 1.5V 1.5V See Figure 1 6 D.U.T. 680 30pF* 3139 drw 03 Figure 1. Output Load * Includes jig and scope capacitances. IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES FUNCTIONAL DESCRIPTION TIMING MODES: IDT STANDARD vs FIRST WORD FALL THROUGH (FWFT) MODE The IDT72805LB/72815LB/72825LB/72835LB/72845LB support two different timing modes of operation. The selection of which mode will operate is determined during configuration at Reset (RS). During a RS operation, the First Load (FL), Read Expansion Input ( RXI) and Write Expansion Input (WXI) pins are used to select the timing mode per the truth table shown in Table 3. In IDT Standard Mode, the first word written to an empty FIFO will not appear on the data output lines unless a specific read operation is performed. A read operation, which consists of activating Read Enable (REN) and enabling a rising Read Clock (RCLK) edge, will shift the word from internal memory to the data output lines. In FWFT mode, the first word written to an empty FIFO is clocked directly to the data output lines after three transitions of the RCLK signal. A REN does not have to be asserted for accessing the first word. Various signals, both input and output signals operate differently depending on which timing mode is in effect. IDT STANDARD MODE In this mode, the status flags, FF, PAF, HF, PAE and EF operate in the manner outlined in Table 1. To write data into to the FIFO, Write Enable (WEN) must be LOW. Data presented to the DATA IN lines will be clocked into the FIFO on subsequent transitions of the Write Clock (WCLK). After the first write is performed, the Empty Flag (EF) will go HIGH. Subsequent writes will continue to fill up the FIFO. The Programmable Almost-Empty flag (PAE) will go HIGH after n + 1 words have been loaded into the FIFO, where n is the Empty offset value. The default setting for this value is stated in the footnote of Table 1. This parameter is also user programmable. See section on Programmable Flag Offset Loading. If one continued to write data into the FIFO, and we assumed no read operations were taking place, the Half-Full flag (HF) would toggle to LOW once the 129th (IDT72805LB), 257th (IDT72815LB), 513th (IDT72825LB), 1,025th (IDT72835LB), and 2,049th (IDT72845LB) word respectively was written into the FIFO. Continuing to write data into the FIFO will cause the Programmable Almost-Full flag (PAF) to go LOW. Again, if no reads are performed, the PAF will go LOW after (256-m) writes for the IDT72805LB, (512-m) writes for the IDT72815LB, (1,024-m) writes for the IDT72825LB, (2,048-m) writes for the IDT72835LB and (4,096-m) writes for the IDT72845LB. The offset "m" is the Full offset value. This parameter is also user programmable. See section on Programmable Flag Offset Loading. If there is no Full offset specified, the PAF will be LOW when the device is 31 away from completely full for IDT72805LB, 63 away from completely full for IDT72815LB, and 127 away from completely full for the IDT72825LB/ 72835LB/72845LB. When the FIFO is full, the Full Flag (FF) will go LOW, inhibiting further write operations. If no reads are performed after a reset, FF will go LOW after D writes to the FIFO. D = 256 writes for the IDT72805LB, 512 for the IDT72815LB, 1,024 for the IDT72825LB, 2,048 for the IDT72835LB and 4,096 for the IDT72845LB, respectively. If the FIFO is full, the first read operation will cause FF to go HIGH. Subsequent read operations will cause PAF and the Half-Full flag (HF) to go HIGH at the conditions described in Table 1. If further read operations occur, without write operations, the Programmable Almost-Empty flag (PAE) will go LOW when there are n words in the FIFO, where n is the Empty offset value. If there is no Empty offset specified, the PAE will be LOW when 7 the device is 31 away from completely empty for IDT72805LB, 63 away from completely empty for IDT72815LB, and 127 away from completely empty for IDT72825LB/72835LB/72845LB. Continuing read operations will cause the FIFO to be empty. When the last word has been read from the FIFO, the EF will go LOW inhibiting further read operations. REN is ignored when the FIFO is empty. FIRST WORD FALL THROUGH MODE (FWFT) In this mode, the status flags, IR, PAF, HF, PAE and OR operate in the manner outlined in Table 2. To write data into to the FIFO, WEN must be LOW. Data presented to the DATA IN lines will be clocked into the FIFO on subsequent transitions of WCLK. After the first write is performed, the Output Ready (OR) flag will go LOW. Subsequent writes will continue to fill up the FIFO. PAE will go HIGH after n + 2 words have been loaded into the FIFO, where n is the Empty offset value. The default setting for this value is stated in the footnote of Table 2. This parameter is also user programmable. See section on Programmable Flag Offset Loading. If one continued to write data into the FIFO, and we assumed no read operations were taking place, the HF would toggle to LOW once the 130th (72805LB), 258th (72815LB), 514th (72825LB), 1,026th (72835LB), and 2,050th (72845LB) word respectively was written into the FIFO. Continuing to write data into the FIFO will cause the PAF to go LOW. Again, if no reads are performed, the PAF will go LOW after (257-m) writes for the IDT72805LB, (513-m) writes for the IDT72815LB, (1,025-m) writes for the IDT72825LB, (2,049-m) writes for the IDT72835LB and (4,097-m) writes for the IDT72845LB, where m is the Full offset value. The default setting for this value is stated in the footnote of Table 2. When the FIFO is full, the Input Ready (IR) flag will go HIGH, inhibiting further write operations. If no reads are performed after a reset, IR will go HIGH after D writes to the FIFO. D = 257 writes for the IDT72805LB, 513 for the IDT72815LB, 1,025 for the IDT72825LB, 2,049 for the IDT72835LB and 4,097 for the IDT72845LB. Note that the additional word in FWFT mode is due to the capacity of the memory plus output register. If the FIFO is full, the first read operation will cause the IR flag to go LOW. Subsequent read operations will cause the PAF and HF to go HIGH at the conditions described in Table 2. If further read operations occur, without write operations, the PAE will go LOW when there are n + 1 words in the FIFO, where n is the Empty offset value. If there is no Empty offset specified, the PAE will be LOW when the device is 32 away from completely empty for IDT72805LB, 64 away from completely empty for IDT72815LB, and 128 away from completely empty for IDT72825LB/72835LB/72845LB. Continuing read operations will cause the FIFO to be empty. When the last word has been read from the FIFO, OR will go HIGH inhibiting further read operations. REN is ignored when the FIFO is empty. PROGRAMMABLE FLAG LOADING Full and Empty flag Offset values can be user programmable. The IDT72805LB/72815LB/72825LB/72835LB/72845LB has internal registers for these offsets. Default settings are stated in the footnotes of Table 1 and Table 2. Offset values are loaded into the FIFO using the data input lines D0D11. To load the offset registers, the Load (LD) pin and WEN pin must be held LOW. Data present on D0-D11 will be transferred in to the Empty Offset register on the first LOW-to-HIGH transition of WCLK. By continuing to hold the LD and WEN pin low, data present on D0-D11 will be transferred into the Full Offset register on the next transition of the WCLK. The third transition again writes to the Empty Offset register. Writing all offset registers does not have to occur at one time. One or two offset registers can be written and then IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES by bringing the LD pin HIGH, the FIFO is returned to normal read/write operation. When the LD pin and WEN are again set LOW, the next offset register in sequence is written. The contents of the offset registers can be read on the data output lines Q0-Q11 when the LD pin is set LOW and REN is set LOW. Data can then be read on the next LOW-to-HIGH transition of RCLK. The first transition of RCLK will present the Empty Offset value to the data output lines. The next transition of RCLK will present the Full offset value. Offset register content can be read out in the IDT Standard mode only. It cannot be read in the FWFT mode. SYNCHRONOUS vs ASYNCHRONOUS PROGRAMMABLE FLAG TIMING SELECTION The IDT72805LB/72815LB/72825LB/72835LB/72845LB can be configured during the "Configuration at Reset" cycle described in Table 3 with either asynchronous or synchronous timing for PAE and PAF flags. If asynchronous PAE/PAF configuration is selected (as per Table 3), the PAE is asserted LOW on the LOW-to-HIGH transition of RCLK. PAE is reset to HIGH on the LOW-to-HIGH transition of WCLK. Similarly, the PAF is asserted LOW on the LOW-to-HIGH transition of WCLK and PAF is reset to HIGH on the LOW-to-HIGH transition of RCLK. For detail timing dia- grams, see Figure 13 for asynchronous PAE timing and Figure 14 for asynchronous PAF timing. If synchronous PAE/PAF configuration is selected, the PAE is asserted and updated on the rising edge of RCLK only and not WCLK. Similarly, PAF is asserted and updated on the rising edge of WCLK only and not RCLK. For detail timing diagrams, see Figure 22 for synchronous PAE timing and Figure 23 for synchronous PAF timing. REGISTER-BUFFERED FLAG OUTPUT SELECTION The IDT72805LB/72815LB/72825LB/72835LB/72845LB can be configured during the "Configuration at Reset" cycle described in Table 4 with single, double or triple register-buffered flag output signals. The various combinations available are described in Table 4 and Table 5. In general, going from single to double or triple buffered flag outputs removes the possibility of metastable flag indications on boundary states (i.e, empty or full conditions). The trade-off is the addition of clock cycle delays for the respective flag to be asserted. Not all combinations of register-buffered flag outputs are supported. Register-buffered outputs apply to the Empty Flag and Full Flag only. Partial flags are not effected. Table 4 and Table 5 summarize the options available. TABLE 1 -- STATUS FLAGS FOR IDT STANDARD MODE IDT72805LB 0 1 to n(1) (n + 1) to 128 129 to (256-(m+1))(2) (256-m) to 255 256 Number of Words in FIFO IDT72815LB IDT72825LB 0 1 to n(1) (n + 1) to 256 257 to (512-(m+1))(2) (512-m) to 511 512 0 1 to n(1) (n + 1) to 512 513 to (1,024-(m+1))(2) (1,024-m) to 1,023 1,024 IDT72835LB 0 1 to n(1) (n + 1) to 1,024 1,025 to (2,048-(m+1))(2) (2,048-m) to 2,047 2,048 IDT72845LB 0 1 to n(1) (n + 1) to 2,048 2,049 to (4,096-(m+1))(2) (4,096-m) to 4,095 4,096 FF PAF H H H H H L H H H H L L HF H H H L L L PAE EF L L H H H H L H H H H H NOTES: 1. n = Empty offset (Default Values : IDT72805LB n=31, IDT72815LB n = 63, IDT72825LB/72835LB/72845LB n = 127) 2. m = Full offset (Default Values : IDT72805LB m=31, IDT72815LB m = 63, IDT72825LB/72835LB/72845LB m = 127) TABLE 2 -- STATUS FLAGS FOR FWFT MODE IDT72805LB 0 1 to (n + 1)(1) (n + 2) to 129 130 to (257-(m+1))(2) (257-m) to 256 257 IDT72815LB 0 1 to (n + 1)(1) (n + 2) to 257 258 to (513-(m+1))(2) (513-m) to 512 513 Number of Words in FIFO IDT72825LB IDT72835LB 0 1 to (n + 1)(1) (n + 2) to 513 514 to (1,025-(m+1))(2) (1,025-m) to 1,024 1,025 0 1 to (n + 1)(1) (n + 2) to 1,025 1,026 to (2,049-(m+1))(2) (2,049-m) to 2,048 2,049 IDT72845LB 0 1 to (n + 1)(1) (n + 2) to 2,049 2,050 to (4,097-(m+1))(2) (4,097-m) to 4,096 4,097 IR L L L L L H PAF HF PAE OR H H H H L L H H H L L L L L H H H H H L L L L L NOTES: 1. n = Empty offset (Default Values : IDT72805LB n = 31, IDT72815LB n = 63, IDT72825LB/72835LB/72845LB n = 127) 2. m = Full Offset (Default Values : IDT72805LB m = 31, IDT72815LB m = 63, IDT72825LB/72835LB/72845LB m = 127) 8 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES TABLE 3 -- TRUTH TABLE FOR CONFIGURATION AT RESET FL 0 0 0 0(1) 1 1 1 1(2) RXI 0 0 1 1 0 0 1 1 WXI 0 1 0 1 0 1 0 1 EF/OR Single register-buffered Empty Flag Triple register-buffered Output Ready Flag Double register-buffered Empty Flag Single register-buffered Empty Flag Single register-buffered Empty Flag Triple register-buffered Output Ready Flag Double register-buffered Empty Flag Single register-buffered Empty Flag FF/IR Single register-buffered Full Flag Double register-buffered Input Ready Flag Double register-buffered Full Flag Single register-buffered Full Flag Single register-buffered Full Flag Double register-buffered Input Ready Flag Double register-buffered Full Flag Single register-buffered Full Flag PAE, PAF Asynchronous Asynchronous Asynchronous Asynchronous Synchronous Synchronous Synchronous Asynchronous FIFO TIMING MODE Standard FWFT Standard Standard Standard FWFT Standard Standard NOTES: 1. In a daisy-chain depth expansion, FL is held LOW for the "first load device". The RXI and WXI inputs are driven by the corresponding RXO and WXO outputs of the preceding device. 2. In a daisy-chain depth expansion, FL is held HIGH for members of the expansion other than the "first load device". The RXI and WXI inputs are driven by the corresponding RXO and WXO outputs of the preceding device. TABLE 4 -- REGISTER-BUFFERED FLAG OUTPUT OPTIONS -- IDT STANDARD MODE Empty Flag (EF) Buffered Output Single Single Double Double Full Flag (FF) Buffered Output Single Single Double Double Partial Flags Timing Mode Asynch Sync Asynch Synch Programming at Reset FL RXI WXI 0 1 0 1 0 0 1 1 0 0 0 0 Flag Timing Diagrams Figure 9, 10 Figure 9, 10 Figure 24, 26 Figure 24, 26 TABLE 5 -- REGISTER-BUFFERED FLAG OUTPUT OPTIONS -- FWFT MODE Output Ready (OR) Triple Triple Input Ready (IR) Double Double Partial Flags Asynch Sync Programming at Reset FL RXI WXI 0 1 0 0 1 1 Flag Timing Diagrams Figure 27 Figure 20, 21 9 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES WEN 0 WCLK Selection Writing to offset registers: Empty Offset Full Offset SIGNAL DESCRIPTIONS: INPUTS: DATA IN (D0 - D17) Data inputs for 18-bit wide data. LD 0 CONTROLS: RESET (RSA/RSB) Reset is accomplished whenever the Reset (RSA/RSB) input is taken to a LOW state. During reset, both internal read and write pointers are set to the first location. A reset is required after power-up before a write operation can take place. The Half-Full flag (HFA/HFB) and Programmable AlmostFull flag (PAFA/PAFB) will be reset to HIGH after tRSF. The Programmable Almost-Empty flag (PAEA/PAEB) will be reset to LOW after tRSF. The Full Flag (FFA/FFB) will reset to HIGH. The Empty Flag (EFA/EFB) will reset to LOW in IDT Standard mode but will reset to HIGH in FWFT mode. During reset, the output register is initialized to all zeros and the offset registers are initialized to their default values. WRITE CLOCK (WCLKA/WCLKB) A write cycle is initiated on the LOW-to-HIGH transition of the Write Clock (WCLKA/WCLKB). Data setup and hold times must be met with respect to the LOW-to-HIGH transition of WCLK. The Write and Read Clocks can be asynchronous or coincident. WRITE ENABLE (WENA/WENB) When the WENA/WENB input is LOW, data may be loaded into the FIFO RAM array on the rising edge of every WCLK cycle if the device is not full. Data is stored in the RAM array sequentially and independently of any ongoing read operation. When WEN is HIGH, no new data is written in the RAM array on each WCLK cycle. To prevent data overflow in the IDT Standard Mode, FF will go LOW, inhibiting further write operations. Upon the completion of a valid read cycle, FF will go HIGH allowing a write to occur. The FF flag is updated on the rising edge of WCLK. To prevent data overflow in the FWFT mode, Input Ready (IRA,IRB) will go HIGH, inhibiting further write operations. Upon the completion of a valid read cycle, IR will go LOW allowing a write to occur. The IR flag is updated on the rising edge of WCLK. WEN is ignored when the FIFO is full in either FWFT or IDT Standard mode. READ CLOCK (RCLKA/RCLKB) Data can be read on the outputs on the LOW-to-HIGH transition of the Read clock (RCLKA/RCLKB), when Output Enable (OEA/OEB) is set LOW. The Write and Read Clocks can be asynchronous or coincident. READ ENABLE (RENA/RENB) When Read Enable (RENA/RENB) is LOW, data is loaded from the RAM array into the output register on the rising edge of every RCLK cycle if the device is not empty. When the REN input is HIGH, the output register holds the previous data and no new data is loaded into the output register. The data outputs Q0-Qn maintain the previous data value. In the IDT Standard mode, every word accessed at Qn, including the first word written to an empty FIFO, must be requested using REN. When the last word has been read from the FIFO, the Empty Flag (EFA/EFB) will go LOW, inhibiting further read operations. REN is ignored when the FIFO is 10 0 1 1 1 0 1 No Operation Write Into FIFO No Operation NOTE: 1. The same selection sequence applies to reading from the registers. REN is enabled and read is performed on the LOW-to-HIGH transition of RCLK. Figure 2. Writing to Offset Registers 17 11 EMPTY OFFSET REGISTER DEFAULT VALUE 001FH (72805) 003FH (72815): 007FH (72825/72835/72845) 17 11 FULL OFFSET REGISTER DEFAULT VALUE 001FH (72805) 003FH (72815): 007FH (72825/72835/72845) 3139 drw 04 0 0 NOTE: 1. Any bits of the offset register not being programmed should be set to zero. Figure 3. Offset Register Location and Default Values empty. Once a write is performed, EF will go HIGH allowing a read to occur. The EF flag is updated on the rising edge of RCLK. In the FWFT mode, the first word written to an empty FIFO automatically goes to the outputs Qn, on the third valid LOW to HIGH transition of RCLK + tSKEW after the first write. REN does not need to be asserted LOW. In order to access all other words, a read must be executed using REN. The RCLK LOW to HIGH transition after the last word has been read from the FIFO, Output Ready (ORA/ORB) will go HIGH with a true read (RCLK with REN = LOW), inhibiting further read operations. REN is ignored when the FIFO is empty. OUTPUT ENABLE (OEA/OEB) When Output Enable (OEA/OEB) is enabled (LOW), the parallel output buffers receive data from the output register. When OE is disabled (HIGH), the Q output data bus is in a high-impedance state. LOAD (LDA/LDB) The IDT72805LB/72815LB/72825LB/72835LB/72845LB devices contain two 12-bit offset registers with data on the inputs, or read on the outputs. When the Load (LDA/LDB) pin is set LOW and WEN is set LOW, data on the inputs D0-D11 is written into the Empty Offset register on the first LOWto-HIGH transition of the Write clock (WCLK). When the LD pin and WEN are held LOW then data is written into the Full Offset register on the second LOW-to-HIGH transition of WCLK. The third transition of WCLK again writes to the Empty Offset register. However, writing all offset registers does not have to occur at one time. One or two offset registers can be written and then by bringing the LD pin HIGH, the FIFO is returned to normal read/write operation. When the LD pin is set LOW, and WEN is LOW, the next offset register in sequence is written. IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES When the LD pin is LOW and WEN is HIGH, the WCLK input is disabled; then a signal at this input can neither increment the write offset register pointer, nor execute a write. The contents of the offset registers can be read on the output lines when the LD pin is set LOW and REN is set LOW; then, data can be read on the LOW-to-HIGH transition of the Read clock (RCLK). The act of reading the control registers employs a dedicated read offset register pointer. (The read and write pointers operate independently). Offset register content can be read out in the IDT Standard mode only. It is inhibited in the FWFT mode. A read and a write should not be performed simultaneously to the offset registers. FIRST LOAD (FLA/FLB) For the single device mode, see Table I for additional information. In the Daisy Chain Depth Expansion configuration, FLA/FLB is grounded to indicate it is the first device loaded and is set to HIGH for all other devices in the Daisy Chain. (See Operating Configurations for further details.) WRITE EXPANSION INPUT (WXIA/WXIB) This is a dual purpose pin. For single device mode, see Table I for additional information. WXIA/WXIB is connected to Write Expansion Out (WXOA/WXOB) of the previous device in the Daisy Chain Depth Expansion mode. READ EXPANSION INPUT (RXIA/RXIB) This is a dual purpose pin. For single device mode, see Table I for additional information. RXIA/RXIB is connected to Read Expansion Out (RXOA/RXOB) of the previous device in the Daisy Chain Depth Expansion mode. EF/OR is synchronous and updated on the rising edge of RCLK. PROGRAMMABLE ALMOST-FULL FLAG (PAFA/PAFB) The Programmable Almost-Full flag (PAFA/PAFB) will go LOW when FIFO reaches the almost-full condition. In IDT Standard mode, if no reads are performed after Reset (RS), the PAF will go LOW after (256-m) writes for the IDT72805LB, (512-m) writes for the IDT72815LB, (1,024-m) writes for the IDT72825LB, (2,048-m) writes for the IDT72835LB and (4,096-m) writes for the IDT72845LB. The offset "m" is defined in the Full Offset register. In FWFT mode, if no reads are performed, PAF will go LOW after (257m) writes for the IDT72805LB, (513-m) writes for the IDT72815LB, (1,025m) writes for the IDT72825LB, (2,049-m) writes for the IDT72835LB and (4,097-m) writes for the IDT72845LB. The default values for m are noted in Table 1 and 2. If asynchronous PAF configuration is selected, the PAF is asserted LOW on the LOW-to-HIGH transition of the Write Clock (WCLK). PAF is reset to HIGH on the LOW-to-HIGH transition of the Read Clock (RCLK). If synchronous PAF configuration is selected (see Table I), the PAF is updated on the rising edge of WCLK. PROGRAMMABLE ALMOST-EMPTY FLAG (PAEA/PAEB) The PAE flag will go LOW when the FIFO reads the almost-empty condition. In IDT Standard mode, PAE will go LOW when there are n words or less in the FIFO. In FWFT mode, the PAE will go LOW when there are n+1 words or less in the FIFO. The offset "n" is defined as the Empty offset. The default values for n are noted in Table 1 and 2. If asynchronous PAE configuration is selected, the PAE is asserted LOW on the LOW-to-HIGH transition of the Read Clock (RCLK). PAE is reset to HIGH on the LOW-to-HIGH transition of the Write Clock (WCLK). If synchronous PAE configuration is selected (see Table I), the PAE is updated on the rising edge of RCLK. WRITE EXPANSION OUT/HALF-FULL FLAG (WXOA/HFA, WXOB/HFB) This is a dual-purpose output. In the Single Device and Width Expansion mode, when Write Expansion In (WXIA/WXIB) and/or Read Expansion In (RXIA/RXIB) are grounded, this output acts as an indication of a half-full memory. After half of the memory is filled, and at the LOW-to-HIGH transition of the next write cycle, the Half-Full flag goes LOW and will remain set until the difference between the write pointer and read pointer is less than or equal to one half of the total memory of the device. The Half-Full flag (HFA/HFB) is then reset to HIGH by the LOW-to-HIGH transition of the Read Clock (RCLK). The HF is asynchronous. In the Daisy Chain Depth Expansion mode, WXI is connected to WXO of the previous device. This output acts as a signal to the next device in the Daisy Chain by providing a pulse when the previous device writes to the last location of memory. READ EXPANSION OUT (RXOA/RXOB) In the Daisy Chain Depth Expansion configuration, Read Expansion In (RXIA/RXIB) is connected to Read Expansion Out (RXOA/RXOB) of the previous device. This output acts as a signal to the next device in the Daisy Chain by providing a pulse when the previous device reads from the last location of memory. DATA OUTPUTS (Q0-Q17, QB0-QB17) Q0-Q17 are data outputs for 18-bit wide data. 11 OUTPUTS: FULL FLAG/INPUT READY (FFA/IRA, FFB/IRB) This is a dual purpose pin. In IDT Standard mode, the Full Flag (FFA/ FFB) function is selected. When the FIFO is full, FF will go LOW, inhibiting further write operations. When FF is HIGH, the FIFO is not full. If no reads are performed after a reset, FF will go LOW after D writes to the FIFO. D = 256 writes for the IDT72805LB, 512 for the IDT72815LB, 1,024 for the IDT72825LB, 2,048 for the IDT72835LB and 4,096 for the IDT72845LB. In FWFT mode, the Input Ready (IRA/IRB) function is selected. IR goes LOW when memory space is available for writing in data. When there is no longer any free space left, IR goes HIGH, inhibiting further write operations. IR will go HIGH after D writes to the FIFO. D = 257 writes for the IDT72805, 513 for the IDT72815, 1,025 for the IDT72825, 2,049 for the IDT72835 and 4,097 for the IDT72845. Note that the additional word in FWFT mode is due to the capacity of the memory plus output register. FF/IR is synchronous and updated on the rising edge of WCLK. EMPTY FLAG/OUTPUT READY (EFA/ORA, EFB/ORB) This is a dual purpose pin. In the IDT Standard mode, the Empty Flag (EFA/EFB) function is selected. When the FIFO is empty, EF will go LOW, inhibiting further read operations. When EF is HIGH, the FIFO is not empty. In FWFT mode, the Output Ready (ORA/ORB) function is selected. OR goes LOW at the same time that the first word written to an empty FIFO appears valid on the outputs. OR stays LOW after the RCLK LOW to HIGH transition that shifts the last word from the FIFO memory to the outputs. OR goes HIGH only with a true read (RCLK with REN = LOW). The previous data stays at the outputs, indicating the last word was read. Further data reads are inhibited until OR goes LOW again. IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 tRS RS tRSR REN, WEN, LD tRSS FL, RXI, WXI (1) COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES tRSR CONFIGURATION SETTING RCLK, WCLK (2) tRSF FF/IR tRSF EF/OR tRSF PAF, WXO/ HF, RXO tRSF PAE tRSF Q0 - Q17 OE = 0 NOTES: 1. Single device mode (FL, RXI, WXI) = (0,0,0), (0,0,1), (0,1,0), (1,0,0), (1,0,1) or (1,1,0). FL, RXI, WXI should be static (tied to VCC or GND). 2. The clocks (RCLK, WCLK) can be free-running asynchronously or coincidentally. 3. After reset, the outputs will be LOW if OE = 0 and tri-state if OE = 1. 3139 drw 05 FWFT Mode IDT Standard Mode OE = 1 (3) Figure 5. Reset Timing(2) tCLKH WCLK tCLK tCLKL tDS tDH D0 - D17 DATA IN VALID tENS WEN tWFF FF tSKEW1 (1) RCLK tENH NO OPERATION tWFF REN 3139 drw 06 NOTES: 1. tSKEW1 is the minimum time between a rising RCLK edge and a rising WCLK edge to guarantee that FF will go HIGH during the current clock cycle. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW1, then FF may not change state until the next WCLK edge. 2. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,1,1), (1,0,0) or (1,1,1) during Reset. Figure 6. Write Cycle Timing with Single Register-Buffered FF (IDT Standard Mode) 12 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES tCLK tCLKH RCLK tENS REN tREF EF tA Q0 - Q17 VALID DATA tCLKL tENH NO OPERATION tREF tOLZ tOHZ tOE tSKEW1(1) OE WCLK WEN 3139 drw 07 NOTES: 1. tSKEW1 is the minimum time between a rising WCLK edge and a rising RCLK edge to guarantee that EF will go HIGH during the current clock cycle. If the time between the rising edge of WCLK and the rising edge of RCLK is less than tSKEW1, then EF may not change state until the next RCLK edge. 2. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,1,1), (1,0,0) or (1,1,1) during Reset. Figure 7. Read Cycle Timing with Single Register-Buffered EF (IDT Standard Mode) WCLK tDS D0 - D17 tENS WEN tFRL(1) tSKEW1 RCLK tREF EF tENS REN tA Q0 - Q17 tOLZ tOE OE 3139 drw 08 D0 (first valid write) D1 D2 D3 D4 tA D0 D1 NOTES: 1. When tSKEW1 minimum specification, tFRL (maximum) = tCLK + tSKEW1. When tSKEW1 < minimum specification, tFRL (maximum) = either 2*tCLK + tSKEW1 or tCLK + tSKEW1. The Latency Timing applies only at the Empty Boundary (EF = LOW). 2. The first word is available the cycle after EF goes HIGH, always. 3. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,1,1), (1,0,0) or (1,1,1) during Reset. Figure 8. First Data Word Latency with Single Register-Buffered EF (IDT Standard Mode) 13 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 NO WRITE NO WRITE COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES WCLK tSKEW1 D0 - D17 tWFF FF (1) tDS DATA WRITE tWFF tSKEW1(1) tDS DATA WRITE tWFF WEN RCLK tENS REN OE LOW tA Q0 - Q17 DATA IN OUTPUT REGISTER DATA READ tA NEXT DATA READ 3139 drw 09 tENH tENS tENH NOTES: 1. tSKEW1 is the minimum time between a rising RCLK edge and a rising WCLK edge to guarantee that FF will go HIGH during the current clock cycle. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW1, then FF may not change state until the next WCLK edge. 2. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,1,1), (1,0,0) or (1,1,1) during Reset. Figure 9. Single Register-Buffered Full Flag Timing (IDT Standard Mode) WCLK tDS D0 - D17 tENS WEN tFRL tSKEW1 RCLK tREF EF tREF tREF (1) tDS DATA WRITE 1 tENH tENS DATA WRITE 2 tENH tFRL tSKEW1 (1) REN OE LOW tA Q0 - Q17 DATA IN OUTPUT REGISTER DATA READ 3139 drw 10 NOTES: 1. When tSKEW1 minimum specification, tFRL (maximum) = tCLK + tSKEW1. When tSKEW1 < minimum specification, tFRL (maximum) = either 2 * tCLK + tSKEW1, or tCLK + tSKEW1. The Latency Timing apply only at the Empty Boundary (EF = LOW). 2. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,1,1), (1,0,0) or (1,1,1) during Reset. Figure 10. Single Register-Buffered Empty Flag Timing (IDT Standard Mode) 14 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES tCLKH WCLK tCLK tCLKL tENS LD tENS WEN tDS D0-D15 PAE OFFSET tENH tDH PAE OFFSET PAF OFFSET D0-D11 3139 drw 11 Figure 11. Write Programmable Registers (IDT Standard and FWFT Modes) tCLK tCLKH RCLK tENS LD tENS REN tA Q0-Q15 UNKNOWN PAE OFFSET PAF OFFSET 3139 drw 12 tCLKL tENH PAE OFFSET Figure 12. Read Programmable Registers (IDT Standard Mode) tCLKH WCLK tCLKL tENS WEN n words in FIFO(2), n + 1 words in FIFO(3) tENH tPAEA PAE n + 1 words in FIFO(2), n + 2 words in FIFO(3) n words in FIFO(2), n + 1 words in FIFO(3) tPAEA RCLK tENS REN NOTES: 1. n = PAE offset. 2. For IDT Standard Mode. 3. For FWFT Mode. 4. PAE is asserted LOW on RCLK transition and reset to HIGH on WCLK transition. 5. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,0,1), (0,1,0), (0,1,1) or (1,1,1) during Reset. 3139 drw 13 Figure 13. Asynchronous Programmable Almost-Empty Flag Timing (IDT Standard and FWFT Modes) 15 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES tCLKH WCLK tCLKL (1) tENS WEN tENH tPAFA PAF D - (m + 1) words in FIFO D - m words in FIFO tPAFA RCLK tENS REN 3139 drw 14 D - (m + 1) words in FIFO NOTES: 1. m = PAF offset. 2. D = maximum FIFO Depth. In IDT Standard Mode: D = 256 for the IDT72805, 512 for the IDT72815, 1,024 for the IDT72825, 2,048 for the IDT72835 and 4,096 for the IDT72845. In FWFT Mode: D = 257 for the IDT72805, 513 for the IDT72815, 1,025 for the IDT72825, 2,049 for the IDT72835 and 4,097 for the IDT72845. 3. PAF is asserted to LOW on WCLK transition and reset to HIGH on RCLK transition. 4. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,0,1), (0,1,0), (0,1,1) or (1,1,1) during Reset. Figure 14. Asynchronous Programmable Almost-Full Flag Timing (IDT Standard and FWFT Modes) tCLKH WCLK tCLKL tENH tENS WEN tHF HF D/2 words in FIFO(2), D/2 + 1 words in FIFO(2), [ D-1 + 1] words in FIFO(3) 2 [ D-1 (3) 2 + 2] words in FIFO D/2 words in FIFO(2), [D-1 2 + 1] words in FIFO(3) tHF RCLK tENS REN 3139 drw 15 NOTES: 1. D = maximum FIFO Depth. In IDT Standard Mode: D = 256 for the IDT72805, 512 for the IDT72815, 1,024 for the IDT72825, 2,048 for the IDT72835 and 4,096 for the IDT72845. In FWFT Mode: D = 257 for the IDT72805, 513 for the IDT72815, 1,025 for the IDT72825, 2,049 for the IDT72835 and 4,097 for the IDT72845. 2. For IDT Standard Mode. 3. For FWFT Mode. 4. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,0,1), (0,1,0), (1,0,0), (1,0,1) or (1,1,0) during Reset. Figure 15. Half-Full Flag Timing (IDT Standard and FWFT Modes) 16 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES tCLKH WCLK Note 1 tXO tXO WXO tENS WEN 3139 drw 16 NOTE: 1. Write to Last Physical Location. Figure 16. Write Expansion Out Timing tCLKH RCLK Note 1 tXO tXO RXO tENS REN NOTE: 1. Read from Last Physical Location. 3139 drw 17 Figure 17. Read Expansion Out Timing tXI WXI tXIS WCLK 3139 drw 18 Figure 18. Write Expansion In Timing tXI RXI tXIS RCLK 3139 drw 19 Figure 19. Read Expansion In Timing 17 WCLK 1 1 tENS tDS W3 W4 W[D-m-2] W[D-m-1] W[D-m] W[D-m+1] W[D-m+2] W[D-1] tSKEW2 2 3 (2) WEN tDS W[n +2] W[n+3] W[n+4] W[ WD D-1 tDS tDH tDS W[ D-1 tENH D0 - D17 W1 W2 ] ] W[ D-1 ] tSKEW1 RCLK 1 REN tA W1 tREF Q0 - Q17 DATA IN OUTPUT REGISTER OR tPAES PAE HF tHF IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 18 PAF tPAFS IR tWFF 3139 drw 20 NOTES: 1. tSKEW1 is the minimum time between a rising WCLK edge and a rising RCLK edge for OR to go LOW after two RCLK cycles plus tREF. If the time between the rising edge of WLCK and the rising edge of RCLK is less than tSKEW1, then the OR deassertion may be delayed one extra RCLK cycle. 2. tSKEW2 is the minimum time between a rising WCLK edge and a rising RCLK edge for PAE to go HIGH during the current clock cycle. If the time between the rising edge of WCLK and the rising edge of RCLK is less than tSKEW2, then the PAE deassertion may be delayed one extra RCLK cycle. 3. LD = HIGH, OE = LOW 4. n = PAE offset, m = PAF offset, D = maximum FIFO depth = 257 words for the IDT72805, 513 words for the IDT72815, 1,025 words for the IDT72825, 2,049 words for the IDT72835 and 4,097 words for the IDT72845. 5. Select this mode by setting (FL, RXI, WXI) = (1,0,1) during Reset. COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES Figure 20. Write Timing with Synchronous Programmable Flags (FWFT Mode) WCLK 2 tSKEW2 (2) tENS tENH 1 (1) tSKEW1 WEN tDS tDH D0 - D17 WD RCLK 1 tENS tENS REN OE tA tA tA W3 Wm+2 W[m+3] W[D-1] W[m+4] W[D-n-1] W[D-n+1] W[D-n+2] W[D-n] W[ D-1 W2 tA tA tA WD tREF tOHZ tOE Q0 - Q17 W1 W1 ] W[ D-1 ] OR tPAES PAE HF tPAFS tHF IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 19 tWFF PAF tWFF IR 3139 drw 21 NOTES: 1. tSKEW1 is the minimum time between a rising RCLK edge and a rising WCLK edge to guarantee that IR will go LOW after one WCLK plus tWFF. If the time between the rising edge of RLCK and the rising edge of WCLK is less than tSKEW1, then the IR assertion may be delayed an extra WCLK cycle. 2. tSKEW2 is the minimum time between a rising RCLK edge and a rising WCLK edge for PAF to go HIGH during the current clock cycle. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW2, then the PAF deassertion time may be delayed an extra WCLK cycle. 3. LD = HIGH 4. n = PAE offset, m = PAF offset, D = maximum FIFO depth = 257 words for the IDT72805, 513 words for the IDT72815, 1,025 words for the IDT72825, 2,049 words for IDT72835 and 4,097 words for IDT72845. 5. Select this mode by setting (FL, RXI, WXI) = (1,0,1) during Reset. COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES Figure 21. Read Timing with Synchronous Programmable Flags (FWFT Mode) IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 tCLKH WCLK tENS WEN n words in FIFO(2), n + 1words in FIFO(3) tSKEW2 (4) RCLK tENS REN tENH tPAES tENH tCLKL COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES PAE n + 1 words in FIFO(2), n + 2 words in FIFO(3) tPAES n Words in FIFO(2), n + 1 words in FIFO(3) 3139 drw 22 NOTES: 1. n = PAE offset. 2. For IDT Standard Mode. 3. For FWFT Mode. 4. tSKEW2 is the minimum time between a rising WCLK edge and a rising RCLK edge for PAE to go HIGH during the current clock cycle. If the time between the rising edge of WCLK and the rising edge of RCLK is less than tSKEW2, then the PAE deassertion may be delayed one extra RCLK cycle. 5. PAE is asserted and updated on the rising edge of RCLK only. 6. Select this mode by setting (FL, RXI, WXI) = (1,0,0), (1,0,1), or (1,1,0) during Reset. Figure 22. Synchronous Programmable Almost-Empty Flag Timing (IDT Standard and FWFT Modes) tCLKH WCLK tCLKL tENS WEN tENH tPAFS PAF D-(m+1) Words in FIFO tPAFS RCLK tENS REN tENH 3139 drw 23 D - m Words in FIFO tSKEW2 (3) D -(m+1) Words in FIFO NOTES: 1. m = PAF offset. 2. D = maximum FIFO Depth. In IDT Standard Mode: D = 256 for the IDT72805, 512 for the IDT72815, 1,024 for the IDT72825, 2,048 for the IDT72835 and 4,096 for the IDT72845. In FWFT Mode: D = 257 for the IDT72805, 513 for the IDT72815, 1,025 for the IDT72825, 2,049 for the IDT72835 and 4,097 for the IDT72845. 3. tSKEW2 is the minimum time between a rising RCLK edge and a rising WCLK edge for PAF to go HIGH during the current clock cycle. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW2, then the PAF deassertion time may be delayed an extra WCLK cycle. 4. PAF is asserted and updated on the rising edge of WCLK only. 5. Select this mode by setting (FL, RXI, WXI) = (1,0,0), (1,0,1), or (1,1,0) during Reset. Figure 23. Synchronous Programmable Almost-Full Flag Timing (IDT Standard and FWFT Modes) 20 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 NO WRITE NO WRITE 1 tSKEW1 (1) COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES WCLK D0 - D17 2 tDS Wd tWFF tWFF tSKEW1 (1) 1 2 DATA WRITE tDS tWFF FF WEN RCLK tENS tENH tENS tENH REN OE LOW tA tA DATA READ NEXT DATA READ 3139 drw 24 Q0 - Q17 DATA IN OUTPUT REGISTER NOTES: 1. tSKEW1 is the minimum time between a rising RCLK edge and a rising WCLK edge to guarantee that FF will go HIGH after one WCLK cycle plus tWFF. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW1, then the FF deassertion time may be delayed an extra WCLK cycle. 2. LD = HIGH. 3. Select this mode by setting (FL, RXI, WXI) = (0,1,0) or (1,1,0) during Reset. Figure 24. Double Register-Buffered Full Flag Timing (IDT Standard Mode) tCLKH tCLK tCLKL 2 tDS tDH WCLK D0 - D17 1 DATA IN VALID tENS tENH NO OPERATION WEN tWFF tWFF FF tSKEW1(1) RCLK REN 3139 drw 25 NOTES: 1. tSKEW1 is the minimum time between a rising RCLK edge and a rising WCLK edge to guarantee that FF will go HIGH after one WCLK cycle plus tRFF. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW1, then the FF deassertion may be delayed an extra WCLK cycle. 2. LD = HIGH. 3. Select this mode by setting (FL, RXI, WXI) = (0,1,0) or (1,1,0) during Reset. Figure 25. Write Cycle Timing with Double Register-Buffered FF (IDT Standard Mode) 21 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES tCLK tCLKH tCLKL RCLK tENS tENH NO OPERATION tREF 1 2 REN EF tA tREF Q0 - Q17 tOLZ tOE LAST WORD tOHZ OE tSKEW1 (1) WCLK tENH tENS WEN tDS tDH D0 - D17 FIRST WORD 3139 drw 26 NOTES: 1. tSKEW1 is the minimum time between a rising WCLK edge and a rising RCLK edge to guarantee that EF will go HIGH after one RCLK cycle plus tREF. If the time between the rising edge of WCLK and the rising edge of RCLK is less than tSKEW1. then the EF deassertion may be delayed an extra RCLK cycle. 2. LD = HIGH 3. Select this mode by setting (FL, RXI, WXI) = (0,1,0) or (1,1,0) during Reset. Figure 26. Read Cycle Timing with Double Register-Buffered EF (IDT Standard Timing) WCLK tENS WEN tENH tDS D0 tDH W1 W2 tSKEW1 (1) tDS W3 W4 W[n +2] W[n+3] - D17 RCLK 1 2 3 REN tA Q0 - Q17 DATA IN OUTPUT REGISTER W1 tREF tREF 3139 drw 27 OR NOTES: 1. tSKEW1 is the minimum time between a rising WCLK edge and a rising RCLK edge for OR to go HIGH during the current cycle. If the time between the rising edge of WLCK and the rising edge of RCLK is less than tSKEW1, then the OR deassertion may be delayed one extra RCLK cycle. 2. LD = HIGH, OE = LOW 3. Select this mode by setting (FL, RXI, WXI) = (0,0,1) or (1,0,1) during Reset. Figure 27. OR Flag Timing and First Word Fall Through when FIFO is Empty (FWFT mode) 22 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES OPERATING CONFIGURATIONS SINGLE DEVICE CONFIGURATION Each of the two FIFOs contained in a single IDT72805LB/72815LB/ 72825LB/72835LB/72845LB may be used as a stand-alone device when the application requirements are for 256/512/1,024/2,048/4,096 words or less. These FIFOs are in a single Device Configuration when the First Load (FL), Write Expansion In (WXI) and Read Expansion In (RXI) control inputs are configured as (FL, RXI, WXI = (0,0,0), (0,0,1), (0,1,0), (1,0,0), (1,0,1) or (1,1,0) during reset (Figure 28). RESET (RS) WRITE CLOCK (WCLK) WRITE ENABLE (WEN) LOAD (LD) DATA IN (D0 - D17) FULL FLAG/INPUT READY (FF/IR) PROGRAMMABLE (PAE) HALF-FULL FLAG (HF) FL RXI WXI IDT 72805 72815 72825 72835 72845 FIFO A OR B READ CLOCK (RCLK) READ ENABLE (REN) OUTPUT ENABLE (OE) DATA OUT (Q0 - Q17) EMPTY FLAG/OUTPUT READY (EF/OR) PROGRAMMABLE (PAF) 3139 drw 28 Figure 28. Block Diagram of Single 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18, 4,096 x 18 Synchronous FIFO (One of the two FIFOs contained in the IDT72805LB/72815LB/72825LB/72835LB/72845LB) WIDTH EXPANSION CONFIGURATION Word width may be increased simply by connecting together the control signals of FIFO A and B. Status flags can be detected from any one device. The exceptions are the Empty Flag/Output Ready and Full Flag/Input Ready. Because of variations in skew between RCLK and WCLK, it is possible for flag assertion and deassertion to vary by one cycle between FIFOs. To avoid problems the user must create composite flags by gating the Empty Flags/Output Ready of every FIFO, and separately gating all Full RESET (RS) Flags/Input Ready. Figure 29 demonstrates a 36-word width by using one IDT72805LB/72815LB/72825LB/72835LB/72845LBs. Any word width can be attained by adding additional IDT72805LB/72815LB/72825LB/72835LB/ 72845LBs. These FIFOs are in a single Device Configuration when the First Load (FL), Write Expansion In (WXI) and Read Expansion In (RXI) control inputs are configured as (FL, RXI, WXI = (0,0,0), (0,0,1), (0,1,0), (1,0,0), (1,0,1) or (1,1,0) during reset (Figure 29). Please see the Application Note AN-83. RESET (RS) DATA IN (D) 36 18 18 READ CLOCK (RCLK) READ ENABLE (REN) OUTPUT ENABLE (OE) PROGRAMMABLE (PAF) FIFO A FIFO B EMPTY FLAG/OUTPUT READY (EF/OR) WRITE CLOCK (WCLK) WRITE ENABLE (WEN) LOAD (LD) PROGRAMMABLE (PAE) HALF FULL FLAG (HF) FF/IR FULL FLAG/INPUT READY (FF/IR) FL EF/OR WXI RXI 18 FF/IR FL EF/OR WXI RXI 18 DATA OUT (Q) 36 NOTE: 1. Do not connect any output control signals directly together. 3139 drw 29 Figure 29. Block Diagram of the two FIFOs contained in one IDT72805LB/72815LB/72825LB/72835LB/72845LB configured for a 36-bit Width Expansion 23 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES DEPTH EXPANSION CONFIGURATION -- DAISY CHAIN TECHNIQUE (WITH PROGRAMMABLE FLAGS) These devices can easily be adapted to applications requiring more than 256/512/1,024/2,048/4,096 words of buffering. Figure 30 shows Depth Expansion using one IDT72805LB/72815LB/72825LB/72835LB/72845LBs. Maximum depth is limited only by signal loading. Follow these steps: 1.The first device must be designated by grounding the First Load (FL) control input. 2. All other devices must have FL in the HIGH state. 3. The Write Expansion Out (WXO) pin of each device must be tied to the Write Expansion In (WXI) pin of the next device. See Figure 30. 4. The Read Expansion Out (RXO) pin of each device must be tied to the Read Expansion In (RXI) pin of the next device. See Figure 30. 5. All Load (LD) pins are tied together. 6. The Half-Full flag (HF) is not available in this Depth Expansion Configuration. 7. EF, FF, PAE, and PAF are created with composite flags by ORing together every respective flags for monitoring. The composite PAE and PAF flags are not precise. 8. In Daisy Chain mode, the flag outputs are single register-buffered and the partial flags are in asynchronous timing mode. IDT72845 WXOA RXOA WCLKA WENA RCLKA RSA RENA OEA LDA FIFO A 4,096 x 18 DAn QAn Vcc FLA FFA/IRA EFA/ORA PAEA PAFA WXIA DATA IN WRITE CLOCK WRITE ENABLE RESET LOAD FF/IR WXOB RXOB WCLKB RCLKB WENB RSB DBn LDB FIFO B 4,096 x 18 FFA/IRA EFA/ORA EF/OR RENB OEB QBn RXIA DATA OUT READ CLOCK READ ENABLE OUTPUT ENABLE PAF PAFB WXIB FIRST LOAD (FL) PAEB RXIB PAE 3139 drw 30 Figure 30. Block Diagram of 8,192 x 18 Synchronous FIFO Memory With Programmable Flags used in Depth Expansion Configuration 24 IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES DEPTH EXPANSION CONFIGURATION (FWFT MODE) In FWFT mode, the FIFOs can be connected in series (the data outputs of one FIFO connected to the data inputs of the next) with no external logic necessary. The resulting configuration provides a total depth equivalent to the sum of the depths associated with each single FIFO. Figure 31 shows a depth expansion using one IDT72805LB/72815LB/72825LB/72835LB/ 72845LB devices. Care should be taken to select FWFT mode during Master Reset for all FIFOs in the depth expansion configuration. The first word written to an empty configuration will pass from one FIFO to the next ("ripple down") until it finally appears at the outputs of the last FIFO in the chain-no read operation is necessary but the RCLK of each FIFO must be free-running. Each time the data word appears at the outputs of one FIFO, that device's OR line goes LOW, enabling a write to the next FIFO in line. For an empty expansion configuration, the amount of time it takes for OR of the last FIFO in the chain to go LOW (i.e. valid data to appear on the last FIFO's outputs) after a word has been written to the first FIFO is the sum of the delays for each individual FIFO: (N - 1)*(4*transfer clock) + 3*TRCLK where N is the number of FIFOs in the expansion and TRCLK is the RCLK period. Note that extra cycles should be added for the possibility that the tSKEW1 specification is not met between WCLK and transfer clock, or RCLK and transfer clock, for the OR flag. The "ripple down" delay is only noticeable for the first word written to an empty depth expansion configuration. There will be no delay evident for subsequent words written to the configuration. The first free location created by reading from a full depth expansion configuration will "bubble up" from the last FIFO to the previous one until it finally moves into the first FIFO of the chain. Each time a free location is created in one FIFO of the chain, that FIFO's IR line goes LOW, enabling the preceding FIFO to write a word to fill it. For a full expansion configuration, the amount of time it takes for IR of the first FIFO in the chain to go LOW after a word has been read from the last FIFO is the sum of the delays for each individual FIFO: (N - 1)*(3*transfer clock) + 2 TWCLK where N is the number of FIFOs in the expansion and TWCLK is the WCLK period. Note that extra cycles should be added for the possibility that the tSKEW1 specification is not met between RCLK and transfer clock, or WCLK and transfer clock, for the IR flag. The Transfer Clock line should be tied to either WCLK or RCLK, whichever is faster. Both these actions result in data moving, as quickly as possible, to the end of the chain and free locations to the beginning of the chain. HF PAF WRITE CLOCK WRITE ENABLE INPUT READY TRANSFER CLOCK WCLK WEN IR 72805 72815 72825 72835 72845 RCLK OR REN OE Qn FL (0,1) RXI WXI VCC GND n Dn FL (0,1) RXI WXI WCLK WEN IR 72805 72815 72825 72835 72845 RCLK REN OR OE Qn HF PAE READ CLOCK READ ENABLE OUTPUT READY OUTPUT ENABLE n DATA OUT DATA IN n Dn 3139 drw 31 GND GND VCC Figure 31. Block Diagram of 512 x 18, 1,024 x 18, 2,048 x 18, 4,096 x 18, 8,192 x 18 Synchronous FIFO Memory With Programmable Flags used in Depth Expansion Configuration 25 ORDERING INFORMATION IDT XXXXX Device Type X Power XX Speed X Package X Process / Temperature Range BLANK I(1) BG(2) PF 10 15 20 LB 72805 72815 72825 72835 72845 NOTES: 1. Industrial temperature range product for the 15ns speed grade is available as a standard device. 2. The PBGA is only available for the IDT72805LB/72815LB/72825LB in the 15 or 25 ns speed grade. Commercial (0C to +70C) Industrial (-40C to +85C) Ball Grid Array (PBGA, BG121-1) Thin Quad Flatpack (TQFP, PK128-1) Commercial Only Com'l & Ind'l Commercial Only Low Power 256 x18 Dual SyncFIFO 512 x18 Dual SyncFIFO 1,024 x18 Dual SyncFIFO 2,048 x18 Dual SyncFIFO 4,096 x18 Dual SyncFIFO 3139 drw32 Clock Cycle Time (tCLK) Speed in Nanoseconds DATASHEET DOCUMENT HISTORY 05/01/2001 02/12/2003 pgs. 1, 5, 6, and 26. pgs. 1, 2, and 26 CORPORATE HEADQUARTERS 2975 Stender Way Santa Clara, CA 95054 for SALES: 800-345-7015 or 408-727-6116 fax: 408-492-8674 www.idt.com 26 for Tech Support: 408-330-1753 email: FIFOhelp@idt.com |
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