Measurement Computing Digital488 - Manual (Page 20)

Section 2 Getting Started
2.4
2.3 Digital Input/Output Ports
The Digital488 has 40 data lines which can be programmed in groups of 8 as
either input or output. At power on, all 40 bits are in the input mode. Each 8 bit group
is one port, beginning with Port 1 as the least significant 8 bits, and Port 5 as the most
significant 8 bits.
2.3.1 Logic Levels
The data and handshake output lines will drive two TTL loads. In
addition, ports 1 and 2 outputs are 5 Volt CMOS compatible. All input lines are
less than 1.5 TTL loads. All inputs are protected against damage due to high
static voltages. Normal precautions should be taken to limit the input voltages
to -0.3 to +7.0 volts. All I/O lines are referenced to COMMON (Pin 50).
2.3.2 Digital I/O Port Pin Outs
The following diagram illustrates the digital I/O edge connector as view
from the rear of the Digital488 and the top PC Board edge view of the
Digital488OEM.
Digital488 Rear Panel I/O Connector Pin Out
2 10 20 30 40 50
49 39 19 9 1 29
Clear (O)
Trigger (O)
Service (I)
+5 Volts
[ 50 mA Max!]
Not Used
External Data Ready (I)
Inhibit (O)
Data Strobe (O)
Not Used
Common (GND)
Digital I/O
Bits 1 thru 40
(I)
(O)
= Input
= Output