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Operation Theory 25

72XX Series

User’s Manual

4 Operation Theory

4.1 Digital I/O Ports

4.1.1 Introduction

The 7248/96 products can emulate one/two/four mode 0 configu-

ration of 8255 programmable peripheral interface (PPI) chips.

There are 24 DIO signals for every PPI.

4.1.2 8255 Mode 0

The basic functions of 8255 mode 0 are:

 Two 8-bit I/O ports-port A (PA) and port B (PB)

 Two nibble-wide (4-bit) ports C-PC upper and PC lower

 Each port can be used as either input or output

 Outputs are latched whereas inputs are buffered

 16 different input/output configurations are available

4.1.3 Special Function of the DIO Signals

Two I/O signals (PC0 and PC3) of CN1 and CN2 can be used to

generate hardware interrupt. Refer to section 4.3 for details on the

interrupt control. In addition, the P1C4 signals can be used as

input signal of event counter.

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ADLINK Technology 72XX Series Manual do Utilizador Página 39