Advantech PCI-1757UP, Руководство пользователя

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PCI-1757UP User Manual 16
Chapter 3 Operation
3.1 Overview
This chapter describes how to operate PCI-1757UP. The driver software
provided allows a user to access all of the card's functions without regis-
ter level programming. Please see the User's Manual for the driver bun-
dled with this card for more information. For those who prefer to
implement their own bit-level programming to drive the card's functions,
information useful for making such a program is included in this chapter.
3.2 Digital I/O Ports
3.2.1 Introduction
PCI-1757UP emulates one 8255 programmable peripheral interface (PPI)
chip in mode 0, but with higher driving capability than a standard 8255
chip. Each of the 8255 chips has 24 programmable I/O pins that are
divided into three 8-bit ports, designated PA, PB and PC. Each port can
be programmed as an input or an output port. The I/O pins in port A are
designated PA0, PA1,..., PA7; the pins in port B are designated PB0,
PB1,..., PB7, etc. These port names are used both in this manual and in
the software library. Refer to Section 2.4, Pin Assignments.
3.2.2 8255 Mode 0
The basic functions of 8255 mode 0 include:
• Two 8-bit I/O ports - port A (PA) and port B (PB)
• Port C is divided into two nibble-wide (4-bit) I/O ports: PC upper and
PC lower
• Any port can be used for either input or output.
• Output status can be read back.