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General Description

This 8-bit TRI-STATE shift/storage register utilizes advanced

silicon-gate CMOS technology. Along with the low power

consumption and high noise immunity of standard CMOS

integrated circuits, it has the ability to drive 15 LS-TTL

loads. This circuit also features operating speeds comparable to the equivalent low power Schottky device.

The MM54HC299/MM74HC299 features multiplexed inputs/outputs to achieve full 8-bit data handling in a single

20-pin package. Due to the large output drive capability and

TRI-STATE feature, this device is ideally suited for interfacing with bus lines in a bus oriented system.

Two function select inputs and two output control inputs are

used to choose the mode of operation as listed in the function table. Synchronous parallel loading is accomplished by

taking both function select lines S0 and S1 high. This places

the TRI-STATE outputs in a high impedance state, which

permits data applied to the input/output lines to be clocked

into the register. Reading out of the register can be done

while the outputs are enabled in any mode. A direct overriding CLEAR input is provided to clear the register whether

the outputs are enabled or disabled.

The 54HC/74HC logic family is functionally as well as pinout

compatible with the standard 54LS/74LS logic family. All

inputs are protected from damage due to static discharge by

internal diode clamps to VCC and ground.

Features

Y Typical operating frequency 40 MHz

Y Typical propagation delay: 20 ns

Y Low quiescent current: 80 mA maximum (74HC)

Y High output drive for bus applications

Y Low quiescent current: 1 mA maximum