Digital488/80A Overview
1
Introduction…… 1
Addressing Modes…… 1
Digital I/O Lines…… 1
Handshaking/Control Lines…… 1
HVCX1 High Voltage/Current Interface Option…… 2
Power-Up & Setup Configuration…… 2
Internal Buffer…… 2
Software Programmable Features…… 2
Accessories…… 2
Specifications…… 3
Digital I/O…… 3
IEEE 488…… 3
General…… 3
Data Transfer Speeds…… 4
Introduction
The Digital488/80A is a digital input and output interface to the IEEE 488 bus that enables an IEEE 488
controller to program 80 bits of TTL level signals as either inputs or outputs. It includes six
handshake/control lines for each 40-bit channel and two addressing modes. The unit is fully
programmable, including the power-up configuration, which is stored in non-volatile RAM. The internal
data buffer in the Digital488/80A can store up to 2,000 40-byte words. With the addition of the HVCX1
High Current/High Voltage Interface option, the I/O lines can be configured as high voltage inputs or as
high current/high voltage outputs to allow interfacing with solenoids, switching relays and other high
voltage/high current devices.
Addressing Modes
Two addressing modes are available in the Digital488/80A. Dual primary addressing permits two channels
to reside at two consecutive primary IEEE 488 bus addresses. Secondary addressing allows two channels
to reside at the same primary IEEE 488 bus address with two consecutive secondary addresses.
When addressed to Talk, the Digital488/80A outputs data from all forty bits of the selected channel or a
selected eight bit port. When addressed to Listen, the unit accepts input data and programming information
from the controller and outputs the data to the appropriate I/O port.
Digital I/O Lines
The Digital488/80A has 80 TTL level digital I/O lines that are divided into two 40-bit channels. Each
channel is divided into five eight-bit ports. Six high level ASCII commands configure the ports to be all
inputs, all outputs or combinations in between. Thus, a configuration can range from 80 input lines to 80
output lines or combinations in between in multiples of 8 bits.
Handshaking/Control Lines
Each 40-bit channel has six handshaking/control lines. The Clear (Pin 41) output line is pulsed whenever a
Device Clear (
DCL
) or Selected Device Clear (
SDC
) command is received from the IEEE 488 controller.
The Data Strobe (Pin 42) output is pulsed when the IEEE 488 controller presents new data on the I/O lines.
The Trigger (Pin 43) output signal is pulsed when a Group Execute Trigger (
GET
) command is received on
the bus. The Inhibit (Pin 44) output line is asserted while the IEEE 488 controller is reading data from
input lines. The Service (Pin 45) line is an edge-triggered input that generates a Service Request on the
bus. The External Data Ready (Pin 46) input line is used to latch digital input data on the I/O lines.
Digital488/80A User’s Manual
Digital488/80A Overview 1
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