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Embedded Systems and Computer Architecture by Graham R Wilson

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Appendix C

Specifications of the input and output devices

Summary

image

Device: Toggle Switches

Data port address: SWS = 0x90

image

Function:

This device is a bank of eight toggle switches. When the data port SWS is read, this device returns a byte of data each bit of which indicates the state of a switch. The current value of the data port is shown in the ‘Output’ box. A switch toggles when clicked.

Example:

image

Device: Keypad

Data port address:

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