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| 10-LINE-TO-4-LINE AND 8-LINE-TO-3-LINE PRIORITY ENCODERS The SN54 / 74LS147 and the SN54 / 74LS148 are Priority Encoders. They provide priority decoding of the inputs to ensure that only the highest order data line is encoded. Both devices have data inputs and outputs which are active at the low logic level. The LS147 encodes nine data lines to four-line (8-4-2-1) BCD. The implied decimal zero condition does not require an input condition because zero is encoded when all nine data lines are at a high logic level. The LS148 encodes eight data lines to three-line (4-2-1) binary (octal). By providing cascading circuitry (Enable Input EI and Enable Output EO) octal expansion is allowed without needing external circuitry. The SN54 / 74LS748 is a proprietary Motorola part incorporating a built-in deglitcher network which minimizes glitches on the GS output. The glitch occurs on the negative going transition of the EI input when data inputs 0 - 7 are at logical ones. The only dc parameter differences between the LS148 and the LS748 are that (1) Pin 10 (input 0) has a fan-in of 2 on the LS748 versus a fan-in of 1 on the LS148; (2) Pins 1, 2, 3, 4, 11, 12 and 13 (inputs 1, 2, 3, 4, 5, 6, 7) have a fan-in of 3 on the LS748 versus a fan-in of 2 on the LS148. The only ac difference is that tPHL from EI to EO is changed from 40 to 45 ns. SN54 / 74LS147 (TOP VIEW) OUTPUT VCC 16 NC 15 D 14 D 4 5 1 4 2 5 6 3 6 7 4 7 8 5 8 C 6 C B 7 B 8 GND 3 13 3 INPUTS 2 12 2 1 11 1 9 10 9 A OUTPUT A 9 SN54/74LS147 SN54/74LS148 SN54/74LS748 10-LINE-TO-4-LINE AND 8-LINE-TO-3-LINE PRIORITY ENCODERS LOW POWER SCHOTTKY J SUFFIX CERAMIC CASE 620-09 16 1 16 1 N SUFFIX PLASTIC CASE 648-08 16 1 D SUFFIX SOIC CASE 751B-03 ORDERING INFORMATION SN54LSXXXJ SN74LSXXXN SN74LSXXXD Ceramic Plastic SOIC INPUTS OUTPUTS SN54 / 74LS148 SN54 / 74LS748 (TOP VIEW) OUTPUTS VCC 16 EO 15 EO 4 5 1 4 2 5 6 3 6 INPUTS 7 4 7 EI 5 E1 A2 6 A2 GS 14 GS 3 13 3 INPUTS 2 12 2 1 11 1 0 10 0 A0 A1 7 A1 8 GND OUTPUT A0 9 OUTPUTS FAST AND LS TTL DATA 5-1 SN54/74LS147 * SN54/74LS148 * SN54/74LS748 SN54 / 74LS148 SN54 / 74LS748 FUNCTION TABLE OUTPUTS 6 H X X X L H H H H H 7 H X X L H H H H H H 8 H X L H H H H H H H 9 H L H H H H H H H H D H L L H H H H H H H C H H H L L L L H H H B H H H L L H H L L H A H L H L H L H L H L EI H L L L L L L L L L 0 X H X X X X X X X L 1 X H X X X X X X L H INPUTS 2 X H X X X X X L H H 3 X H X X X X L H H H 4 X H X X X L H H H H 5 X H X X L H H H H H 6 X H X L H H H H H H 7 X H L H H H H H H H A2 H H L L L L H H H H OUTPUTS A1 H H L L H H L L H H A0 H H L H L H L H L H GS H H L L L L L L L L EO H L H H H H H H H H SN54 / 74LS147 FUNCTION TABLE INPUTS 1 H X X X X X X X X L 2 H X X X X X X X L H 3 H X X X X X X L H H 4 H X X X X X L H H H 5 H X X X X L H H H H H = HIGH Logic Level, L = LOW Logic Level, X = Irrelevant FUNCTIONAL BLOCK DIAGRAMS 1 (11) 0 (12) (9) (13) 2 (1) 3 (2) (7) B 4 A 1 (10) (15) (11) (14) EO GS 2 3 (12) (8) A0 4 5 (13) (1) (7) 6 7 (3) 5 (4) (6) 6 (2) A1 (3) C 8 9 (5) 7 (10) (14) D (4) (5) EI (6) A2 SN54 / 74LS147 SN54 / 74LS148 FAST AND LS TTL DATA 5-2 SN54/74LS147 * SN54/74LS148 * SN54/74LS748 FUNCTIONAL BLOCK DIAGRAMS (continued) G31 (10) 0 (11) 1 G2 (12) 2 G3 (13) 3 G4 4 (1) G5 5 6 (2) G6 (3) G7 7 EI (4) G8 (5) G1 G12 G11 G10 G9 G13 (15) (14) G29 (9) G18 EO GS A0 (7) G23 A1 (6) G28 A2 SN54 / 74LS748 FAST AND LS TTL DATA 5-3 SN54/74LS147 * SN54/74LS148 * SN54/74LS748 GUARANTEED OPERATING RANGES Symbol VCC TA IOH IOL Supply Voltage Operating Ambient Temperature Range Output Current -- High Output Current -- Low Parameter 54 74 54 74 54, 74 54 74 Min 4.5 4.75 - 55 0 Typ 5.0 5.0 25 25 Max 5.5 5.25 125 70 - 0.4 4.0 8.0 Unit V C mA mA DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified) Limits Symbol S bl VIH VIL VIK VOH Parameter P Input HIGH Voltage 54 Input LOW Voltage 74 Input Clamp Diode Voltage 54 Output HIGH Voltage 74 54, 74 VOL Output LOW Voltage 74 Input HIGH Current All Others Input 0 (LS748) Inputs 1 - 7 (LS148) Inputs 1 - 7 (LS748) All Others Input 0 (LS748) Inputs 1 - 7 (LS148) Inputs 1 - 7 (LS748) Input LOW Current All Others Input 0 (LS748) Inputs 1 - 7 (LS148) Inputs 1 - 7 (LS748) Short Circuit Current (Note 1) Power Supply Current Output HIGH Output LOW - 20 0.35 0.5 20 40 40 60 0.1 0.2 0.2 0.3 - 0.4 - 0.8 - 0.8 - 1.2 - 100 17 20 V 2.7 3.5 0.25 0.4 V V 2.5 - 0.65 3.5 0.8 - 1.5 V V Min 2.0 0.7 V Typ Max Unit Ui V Test C di i T Conditions Guaranteed Input HIGH Voltage for All Inputs Guaranteed Input LOW Voltage for p g All Inputs VCC = MIN, IIN = - 18 mA VCC = MIN, IOH = MAX, VIN = VIH , , or VIL per Truth Table IOL = 4.0 mA IOL = 8.0 mA VCC = VCC MIN, VIN = VIL or VIH per Truth Table A VCC = MAX, VIN = 2.7 V IIH mA VCC = MAX, VIN = 7.0 V IIL mA VCC = MAX, VIN = 0.4 V IOS ICCH ICCL mA mA mA VCC = MAX VCC = MAX, All Inputs = 4.5 V VCC = MAX, Inputs 7 & E1 = GND All Other Inputs = 4.5 V Note 1: Not more than one output should be shorted at a time, nor for more than 1 second. FAST AND LS TTL DATA 5-4 SN54/74LS147 * SN54/74LS148 * SN54/74LS748 AC CHARACTERISTICS (VCC = 5.0 V, TA = 25C) SN54 / 74LS147 Symbol S bl tPLH tPHL tPLH tPHL Any Any From (Input) Any To (Output) Any Limits Waveform W f In-phase p output Out-of-phase p output Min Typ 12 12 21 15 Max 18 ns 18 33 ns 23 CL = 15 pF, pF, RL = 2.0 k Unit Ui Test C di i T Conditions SN54 / 74LS148 SN54 / 74LS748 Symbol S bl tPLH tPHL tPLH tPHL tPLH tPHL tPLH tPHL tPLH tPHL tPLH tPHL tPLH tPHL EI EO EI GS EI A0, A1, A0 A1 or A2 0 thru 7 GS 0 thru 7 EO 1 thru 7 A0, A1, A0 A1 or A2 From (Input) 1 thru 7 To (Output) A0, A1, A0 A1 or A2 Limits Waveform W f In-phase p output Out-of-phase p output Out-of-phase p output In-phase p output In-phase p output In-phase p output In-phase output Min Typ 14 15 20 16 7.0 25 35 9.0 16 12 12 14 12 28 30 Max 18 ns 25 36 ns 29 18 ns 40 55 ns 21 25 ns 25 17 ns 36 21 40 45 ns (LS148) (LS748) CL = 15 pF F pF, RL = 2.0 k Unit Ui Test C di i T Conditions FAST AND LS TTL DATA 5-5 |
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