National Instruments GPIB-COM GPIB-COM Components

Section Three Function Description

© National Instruments Corporation 3-3 GPIB-COM User Manual

GPIB-COM Components

The interface consists of the following functional components:

• Address Decoding

• Configuration Jumpers

• INS8250A Compatible Registers

• GPIB Acceptor and Source Handshaking

• Mode Control Logic

• Interrupt Control Logic

• Direction Buffers

• GPIB Transceivers

Address Decoding

Address decoding monitors the PC address bus to recognize when a GPIB-COM address is

present and enables a read and/or write to its registers.

Configuration Jumpers

These onboard jumpers select the base address, GPIB controller mode, and interrupt request line

used by the GPIB-COM.

INS8250A Compatible Registers

The main component of an IBM PC compatible serial adapter is an INS8250A Asynchronous

Communications chip or its equivalent, which handles RS-232 communication. The INS8250A

compatible registers on the GPIB-COM emulate the serial adapter registers so that the GPIB-

COM will operate transparently with any serial port driver.

GPIB Acceptor and Source Handshaking

This circuitry converts PC serial port handshaking into GPIB handshaking. This process is

completely software-transparent.

Mode Control Logic

This circuitry determines whether the GPIB-COM should be a Talker (and the target device a

Listener) or a Listener (and the target device a Talker).

Interrupt Control Logic

This circuitry generates and masks interrupts on GPIB conditions which correspond to the

conditions that would cause the INS8250A circuit to generate an interrupt.

Contents

Main Page Page FCC/DOC Radio Frequency Interference Compliance Preface Introduction to the GPIB-COM Organization of This Manual Related Documents Abbreviations Used in This Manual Contents Page Figures Tables Section One Introduction GPIB-COM Characteristics What Your Kit Should Contain Optional Equipment Page Page Switch and Jumper Settings Base I/O Address and Interrupt Selection Talk/Listen Modes Talk/Listen Address and Special Function Selection Page Installation Special Considerations When Using the GPIB-COM filename Page Function Description Section Three GPIB-COM User Manual 3-2 National Instruments Corporation Figure 3-1 shows a block diagram of the GPIB-COM. GPIB Figure 3-1. Block Diagram of GPIB-COM GPIB-COM Components Page Section Four Running Diagnostic Tests The GPIB-COM Test Commands -1 printer test -2 plotter test -c change COM configuration -q quit Section Five Programming the GPIB-COM The GPIB-COM Registers Transmitter Holding Register Receive Buffer Register Divisor Latch Least Significant Byte (LSB) Register Divisor Latch Most Significant Byte (MSB) Register Interrupt Enable Register Page Interrupt Identification Register Line Control Register Page Modem Control Register Page Line Status Register Page Modem Status Register Page Programming the Serial Adapter Polling Method Interrupt-Driven Method The GPIB-COM Controller Function Appendix A Specifications Page Multiline Interface Messages Hex Oct Dec ASCII Msg Hex Oct Dec ASCII Msg Message Definitions Multiline Interface Messages Hex Oct Dec ASCII Msg Hex Oct Dec ASCII Msg Appendix C Operation of the GPIB History of the GPIB Types of Messages Talkers, Listeners, and Controllers System Controller and Active Controller GPIB Signals Appendix C Operation of the GPIB National Instruments Corporation C-3 GPIB-COM User Manual Figure C-1 shows the arrangement of these signals on the GPIB cable connector. Data Lines Handshake Lines NRFD (not ready for data) NDAC (not data accepted) Page Page Page Configuration Restrictions User Comment Form