User manual

PCI-1753/1753E User Manual 18
Chapter 3 Operation
3.1 Overview
This chapter describes the operating characteristics of the PCI-1753/
1753E. The driver software bundled with this card allows a user to
access all of the card's functions without register level programming.
Please see the User's Manual included on the driver CD-ROM for more
information. For users 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
The PCI-1753 and 1753E each emulate four 8255 programmable
peripheral interface (PPI) chips in mode 0, but with higher driving
capability than a standard 8255 chip. Each of these 8255 chip emulators
has 24 programmable I/O pins that are divided into three 8-bit ports. The
total 96 digital I/O pins on either the PCI-1753 or the PCI-1753E are
divided into 12 ports, designated PA0, PB0, PC0, PA1, PB1, PC1, PA2,
PB2, PC2, PA3, PB3 and PC3. Each port can be programmed as an input
or an output port. The I/O pins in port A0 are designated PA00, PA01,...,
PA07; the pins in port B0 are designated PB00, PB01,..., PB07, etc.
These port names are used both in this manual and in the software library.
Please refer to Section 1.5, Pin Assignments.
3.2.2 8255 Mode 0
The basic 8255 mode 0 features included on the PCI-1753/1753E cards
are:
• 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.