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| MC54/74F148 8-LINE TO 3-LINE PRIORITY ENCODER The MC54/74F148 provides three bits of binary coded output representing the position of the highest order active input, along with an output indicating the presence of any active input. It is easily expanded via input and output enables to provide priority encoding over many bits. * Encodes Eight Data Lines in Priority * Provides 3-Bit Binary Priority Code * Input Enable Capability * Signals When Data Present on Any Input * Cascadable for Priority Encoding of n Bits 8-LINE TO 3-LINE PRIORITY ENCODER FASTTM SHOTTKY TTL CONNECTION DIAGRAM DIP (TOP VIEW) VCC 16 EO 15 GS 14 I3 13 I2 12 I1 11 I0 10 A0 9 16 1 J SUFFIX CERAMIC CASE 620-09 16 N SUFFIX PLASTIC CASE 648-08 1 1 I4 2 I5 3 I6 4 I7 5 E1 6 A2 7 A1 8 GND LOGIC DIAGRAM 16 (10) I0 I1 (11) (15) (14) EO GS 1 D SUFFIX SOIC CASE 751B-03 ORDERING INFORMATION MC54FXXXJ MC74FXXXN MC74FXXXD Ceramic Plastic SOIC I2 I3 I4 (12) (9) (13) A0 LOGIC SYMBOL (1) (7) I5 (2) A1 I0 I1 I2 I3 I4 I5 I6 I7 E1 EO I7 E1 NOTE: This diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays. 10 11 12 13 1 2 3 45 I6 (3) A0 A1 A2 GS (4) (5) (6) A2 15 9 7 6 14 VCC = PIN 16 GND = PIN 8 FAST AND LS TTL DATA 4-59 MC54/74F148 GUARANTEED OPERATING RANGES Symbol VCC TA Supply Voltage Operating Ambient Temperature Range Parameter 54, 74 54 74 IOH IOL Output Current -- High Output Current -- Low 54, 74 54, 74 Min 4.5 -55 0 Typ 5.0 25 25 Max 5.5 125 70 -1.0 20 mA mA Unit V C FUNCTIONAL DESCRIPTION The F148 8-input priority encoder accepts data from eight active LOW inputs (I 0-I7) and provides a binary representation on the three active LOW outputs. A priority is assigned to each input so that when two or more inputs are simultaneously active, the input with the highest priority is represented on the output, with input line 7 having the highest priority. A HIGH on the Enable Input (E1) will force all outputs to the inactive (HIGH) state and allow new data to settle without producing FUNCTION TABLE Inputs E1 H L L L L L L L L L I0 X H X X X X X X X L I1 X H X X X X X X L H I2 X H X X X X X L H H I3 X H X X X X L H H H LSB 0 1 2 3 4 5 6 7 E1 'F148 A0 A1 A2 GS EO A0 0 I4 X H X X X L H H H H I5 X H X X L H H H H H I6 X H X L H H H H H H I7 X H L H H H H H H H GS H H L L L L L L L L A0 H H L H L H L H L H Outputs A1 H H L L H H L L H H A2 H H L L L L H H H H EO H L H H H H H H H H MSB 1 2 3 4 5 6 7 E1 'F148 A1 A2 GS erroneous information at the outputs. A Group Signal output (GS) and Enable Output (EO) are provided along with the three priority data outputs (A2, A1, A0). GS is active LOW when any input is LOW; this indicates when any input is active. EO is active LOW when all inputs are HIGH. Using the Enable Output along with the Enable Input allows cascading for priority encoding on any number of input signals. Both EO and GS are in the inactive HIGH state when the Enable Input is HIGH. H = HIGH Voltage Level; L = LOW Voltage Level; X = Don't Care ENABLE A0 A1 A2 A3 FLAG Figure 1. Application: 16-Input Priority Encoder FAST AND LS TTL DATA 4-60 MC54/74F148 DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified) Limits Symbol VIH VIL VIK VOH Parameter Input HIGH Voltage Input LOW Voltage Input Clamp Diode Voltage Output HIGH Voltage 54, 74 74 VOL IIH Output LOW Voltage Input HIGH Current 2.5 2.7 3.4 3.4 0.35 0.5 20 100 IIL IOS ICC I0, E1 I1-I7 Output Short Circuit Current (Note 2) Power Supply Current -60 23 -0.6 -1.2 -150 35 Min 2.0 0.8 -1.2 Typ Max Unit V V V V V V A A mA mA mA mA VCC = MAX, VIN = 0.5 V VCC = MAX, VOUT = 0 V VCC = MAX, VIN = 4.5 V Test Conditions Guaranteed Input HIGH Voltage Guaranteed Input LOW Voltage IIN = -18 mA IOH = -1.0 mA IOH = -1.0 mA IOL = 20 mA VCC = MIN VCC = 4.50 V VCC = 4.75 V VCC = MIN VCC = MAX, VIN = 2.7 V VCC = MAX, VIN = 7.0 V NOTES: 1. For conditions shown as MIN or MAX, use the appropriate value specified under guaranteed operating ranges. 2. Not more than one output should be shorted at a time, nor for more than 1 second. AC CHARACTERISTICS 54/74F TA = +25C VCC = +5.0 V CL = 50 pF Symbol tPLH tPHL tPLH tPHL tPLH tPHL tPLH tPHL tPLH tPHL tPLH tPHL Parameter Propagation Delay In to An Propagation Delay In to EO Propagation Delay In to GS Propagation Delay E1 to An Propagation Delay E1 to GS Propagation Delay E1 to EO Min 3.5 4.0 2.5 2.0 3.0 2.0 3.5 3.0 2.5 3.0 3.0 4.5 Typ 7.0 8.0 5.0 5.5 7.0 6.0 6.5 6.0 5.0 6.0 5.5 8.0 Max 9.0 10.5 6.5 7.5 9.0 8.0 8.5 8.0 7.0 7.5 7.0 10.5 54F TA = -55C to +125C VCC = 5.0 V 10% CL = 50 pF Min 3.5 4.0 2.5 2.0 3.0 2.0 3.5 3.0 2.5 3.0 3.0 4.5 Max 11 13 8.5 9.5 11 10 10.5 10 9.0 10 9.0 13 74F TA = 0C to 70C VCC = 5.0 V 10% CL = 50 pF Min 3.5 4.0 2.5 2.0 3.0 2.0 3.5 3.0 2.5 3.0 3.0 4.5 Max 10 ns 12 7.5 ns 8.5 10 ns 9.0 9.5 ns 9.0 8.0 ns 8.5 8.0 ns 12 Unit FAST AND LS TTL DATA 4-61 |
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