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PCI-1737U/PCI-1739U User Manual 26

Chapter 4 Operation

This chapter describes the operating characteristics of the PCI-1737U/

PCI-1739U. The DLL driver allows a user to access all of the card's func-

tions without register level programming. Please see the User's Manual

for the driver bundled with this card 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.

4.1 Configuration

The PCI-1737U/PCI-1739U emulates 8255 programmable peripheral

interface (PPI) chips in mode 0, but with higher driving capability than a

standard 8255 chip. The 8255 chips has 24 programmable I/O pins that

are divided into three 8-bit ports. The total 24 DI/O pins from both chips

are divided into 3 ports, designated PA0, PB0, PC0. Each port can be pro-

grammed as an input or an output port. The I/O pins in port A0 are desig-

nated 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. Refer to Chapter 1, connector.

Mode 0 of 8255 provides simple input/output functions. No handshaking

is required since data is written directly to or read from a specified port

(see 8255 MODE 0 Function Definitions).

PCI-1737U/PCI-1739U’s read-back function is another useful function

that allows you to monitor each output port.

4.2 8255 Mode 0 Function Definitions

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.

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Advantech PCI-1739U Manual de usuario Pagina 36