HD74HC148
8-to-3-line Octal Priority Encoder
Description
The HD74HC148 encodes eight data lines to three-line (4-2-1) binary (octal). Cascading circuitry (enable
input EI and enable output EO) is provided to allow octal expansion without the need for external circuitry.
The data inputs and outputs are active at the low logic level.
Features
• High Speed Operation: t
pd
(0 - 7 to A
0
- A
2
) = 15 ns typ (C
L
= 50 pF)
• High Output Current: Fanout of 10 LSTTL Loads
• Wide Operating Voltage: V
CC
= 2 to 6 V
• Low Input Current: 1 µA max
• Low Quiescent Supply Current: I
CC
(static) = 4 µA max (Ta = 25°C)
Function Table
Inputs Outputs
EI01234567A
2
A
1
A
0
GS EO
HXXXXXXXXHHHHH
LHHHHHHHHHHHHL
LXXXXXXXLLLLLH
LXXXXXXLHLLHLH
LXXXXXLHHLHLLH
LXXXXL HHHLHHLH
LXXXLHHHHHLLLH
LXXLHHHHHHL HLH
LXL HHHHHHHHL LH
LL HHHHHHHHHHLH
H : High level
L : Low level
X : Irrelevant