Measurement-computing Digital488 Manual do Utilizador descarregar pdf (Página 9)

Section 1 Introduction

1.1

Introduction

1.1 General Description

The

Digital488

is a digital input and output interface to the IEEE 488 bus.

Each unit has 40 TTL level digital I/O lines, which are divided into 5 eight-bit ports.

Each port is software programmable as input or output. The

Digital488OEM

is a

board level interface with the same capabilities as the

Digital488

. All descriptions in

this manual refer to both products unless otherwise stated. When the model number

Digital488

is used in this manual,

Digital488OEM

is also implied.

The

Digital488

has several features which give it versatile interface

capability. A trigger output signal is asserted on the Group Execute Trigger (GET)

command. Edge-triggered inputs can generate a Service Request on the bus. Six data

formats are software programmable, including ASCII hexadecimal, ASCII character,

ASCII binary, binary, high speed binary and ASCII decimal. There are also

individual bit set and bit clear commands. Programmable terminators are provided

to facilitate interfacing to various controllers.

A status mode enables the controller to interrogate the programmed status of

the

Digital488

at any time. A self-test is initiated at power-on which checks for

proper RAM and ROM operation.

When addressed to talk, the

Digital 488

will output data from all forty bits or

a selected 8 bit port. When addressed to listen, the unit will input data and

programming information from the controller, and output the data to the appropriate

I/O port.

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Measurement-computing Digital488 Manual do Utilizador Página 9