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Features

? Buffered Inputs

? Typical Propagation Delay ( In to Output ) = 12ns at

VCC = 5V, CL = 15pF, TA = 25oC

? Fanout (Over Temperature Range)

- Standard Outputs . . . . . . . . . . . . . . . 10 LSTTL Loads

- Bus Driver Outputs . . . . . . . . . . . . . 15 LSTTL Loads

? Wide Operating Temperature Range . . . -55oC to 125oC

? Balanced Propagation Delay and Transition Times

? Significant Power Reduction Compared to LSTTL

Logic ICs

? HC Types

- 2V to 6V Operation

- High Noise Immunity: NIL = 30%, NIH = 30% of VCC

at VCC = 5V

? HCT Types

- 4.5V to 5.5V Operation

- Direct LSTTL Input Logic Compatibility,

VIL= 0.8V (Max), VIH = 2V (Min)

- CMOS Input Compatibility, Il ≤ 1μA at VOL, VOH

Description

The ’HC257 and ’HCT257 are quad 2-input multiplexers

which select four bits of data from two sources under the

control of a common Select Input (S). The Output Enable

input (OE) is active LOW. When OE is HIGH, all of the outputs

(1Y-4Y) are in the high impedance state regardless of

all other input conditions.

Moving data from two groups of registers to four common

output buses is a common use of the 257. The state of the

Select input determines the particular register from which

the data comes. It can also be used as a function generator.