January 1995

2

Philips Semiconductors

Product specification

Dual 4-bit latch

HEF4508B

MSI

DESCRIPTION

The HEF4508B is a dual 4-bit latch, which consists of two

identical independent 4-bit latches with separate strobe

(ST), master reset (MR), output-enable input (EO) and

3-state outputs (O).

With the ST input in the HIGH state, the data on the D

inputs appear at the corresponding outputs provided EO is

LOW. Changing the ST input to the LOW state locks the

data into the latch. A HIGH on the reset line forces the

outputs to a LOW level regardless of the state of the ST

input. The 3-state outputs are controlled by the

output-enable input. A HIGH on EO causes the outputs to

assume a high impedance OFF-state regardless of other

input conditions. This allows the outputs to interface

directly with bus orientated systems. When EO is LOW the

contents of the latches are available at the outputs.

See Family Specifications

Fig.1 Functional diagram.