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 FAST SHOTTKY TTL J SUFFIX CERAMIC CASE 620-09 CONNECTION DIAGRAM DIP (TOP VIEW) VCC EO GS I3 I2 I1 I0 A0 16 15 14 13 12 11 10 9 16 1 N SUFFIX PLASTIC CASE 648-08 16 1 2 3 4 5 6 7 8 I4 I5 I6 I7 E1 A2 A1 GND 1 D SUFFIX SOIC CASE 751B-03 LOGIC DIAGRAM 16 (10) I0 I1 I2 I3 1 (15) (11) (14) EO GS ORDERING INFORMATION MC54FXXXJ MC74FXXXN MC74FXXXD (12) (9) Ceramic Plastic SOIC A0 (13) LOGIC SYMBOL I4 (1) 10 11 12 13 1 (7) I5 I6 I7 (2) 3 4 5 I0 I1 I2 I3 I4 I5 I6 I7 E1 (3) (4) 2 A1 EO A0 A1 A2 GS 15 9 7 6 14 (6) A2 (5) E1 NOTE: This diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays. FAST AND LS TTL DATA 4-59 VCC = PIN 16 GND = PIN 8 MC54/74F148 GUARANTEED OPERATING RANGES Symbol Parameter VCC Supply Voltage TA Operating Ambient Temperature Range Min Typ Max Unit 54, 74 4.5 5.0 5.5 V 54 –55 25 125 °C 74 0 25 70 IOH Output Current — High 54, 74 –1.0 mA IOL Output Current — Low 54, 74 20 mA 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 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. FUNCTION TABLE Inputs E1 I0 I1 I2 I3 Outputs I4 I5 I6 I7 GS A0 A1 A2 EO H H X X X X X X X X H H H H L H H H H H H H H H H H H L L X X X X X X X L L L L L H L X X X X X X L H L H L L H L X X X X X L H H L L H L H L X X X X L H H H L H H L H L X X X L H H H H L L L H H L X X L H H H H H L H L H H L X L H H H H H H L L H H H L L H H H H H H H L H H H H H = HIGH Voltage Level; L = LOW Voltage Level; X = Don’t Care MSB LSB 0 1 2 3 4 5 6 7 E1 0 1 2 3 4 5 6 7 E1 ’F148 A0 A1 A0 ENABLE ’F148 A2 A1 GS A2 EO A0 A1 A3 A2 GS 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 Parameter VIH Input HIGH Voltage VIL Input LOW Voltage VIK Input Clamp Diode Voltage VOH Output HIGH Voltage Typ Max 2.0 Unit Test Conditions V Guaranteed Input HIGH Voltage 0.8 V Guaranteed Input LOW Voltage –1.2 V IIN = –18 mA VCC = MIN 54, 74 2.5 3.4 V IOH = –1.0 mA VCC = 4.50 V 74 2.7 3.4 V IOH = –1.0 mA VCC = 4.75 V 0.5 V IOL = 20 mA VCC = MIN 20 µA VCC = MAX, VIN = 2.7 V 100 µA VCC = MAX, VIN = 7.0 V I0, E1 –0.6 mA I1–I7 –1.2 mA –150 mA VCC = MAX, VOUT = 0 V 35 mA VCC = MAX, VIN = 4.5 V VOL Output LOW Voltage IIH Input HIGH Current IIL Min IOS Output Short Circuit Current (Note 2) ICC Power Supply Current 0.35 -60 23 VCC = MAX, VIN = 0.5 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 Symbol Parameter 54/74F 54F 74F TA = +25°C VCC = +5.0 V CL = 50 pF TA = –55°C to +125°C VCC = 5.0 V ± 10% CL = 50 pF TA = 0°C to 70°C VCC = 5.0 V ± 10% CL = 50 pF Min Typ Max Min Max Min Max tPLH Propagation Delay 3.5 7.0 9.0 3.5 11 3.5 10 tPHL In to An 4.0 8.0 10.5 4.0 13 4.0 12 tPLH Propagation Delay 2.5 5.0 6.5 2.5 8.5 2.5 7.5 tPHL In to EO 2.0 5.5 7.5 2.0 9.5 2.0 8.5 tPLH Propagation Delay 3.0 7.0 9.0 3.0 11 3.0 10 tPHL In to GS 2.0 6.0 8.0 2.0 10 2.0 9.0 tPLH Propagation Delay 3.5 6.5 8.5 3.5 10.5 3.5 9.5 tPHL E1 to An 3.0 6.0 8.0 3.0 10 3.0 9.0 tPLH Propagation Delay 2.5 5.0 7.0 2.5 9.0 2.5 8.0 tPHL E1 to GS 3.0 6.0 7.5 3.0 10 3.0 8.5 tPLH Propagation Delay 3.0 5.5 7.0 3.0 9.0 3.0 8.0 tPHL E1 to EO 4.5 8.0 10.5 4.5 13 4.5 12 Unit ns ns ns ns ns ns FAST AND LS TTL DATA 4-61