HD74HC677
16-bit Address Comparator
Description
The HD74HC677 address comparator simplifies addressing of memory boards and/or other peripheral
devices. The four P inputs are normally hard wired with a preprogrammed address. An internal decoder
determines what input infomation applied to the 16 A inputs must be low or high to cause a low state at the
output (Y). For example, a positive-logic bit combination of 0111 (decimal 7) at the P input determines
that inputs A
1
through A
7
must be low and that inputs A
8
through A
16
must be high to cause the output to go
low. Equality of the address applied at the A inputs to the preprogrammed address is indicated by the
output being low.
The HD74HC677 features an enable input (G). When G is low, the device is enabled. When G is high, the
device is disabled and the output is high regardless of the A and P inputs.
Features
High Speed Operation: t
pd
(A to Y) = 17 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 A max
Low Quiescent Supply Current: I
CC
(static) = 4 A max (Ta = 25C)
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