9 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

In this application, the SN74HCS594 is used to control seven-segment displays. Utilizing the serial output and

combining a few of the input signals, this implementation reduces the number of I/O pins required to control the

displays from sixteen to four. Unlike other I/O expanders, the SN74HCS594 does not need a communication

interface for control. It can be easily operated with simple GPIO pins.

There is no practical limitation to how many SN74HCS594 devices can be cascaded. To add more, the

serial output will need to be connected to the following serial input and the clocks will need to be connected

accordingly. With separate control for the shift registers and output registers, the desired digit can be displayed

while the data for the next digit is loaded into the shift register.

At power-up, the initial state of the shift registers and output registers are unknown. To give them a defined state,

both registers need to be cleared. An RC can be connected to the SRCLR and RCLR pins as shown in the

Typical application block diagram to initialize the shift and output registers to all zeros.

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SN74HCS594

SCLS839A – OCTOBER 2020 – REVISED MAY 2021

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