ICS ELECTRONICS 4863 Manual page 52

2.8 DIGITAL I/O CONNECTIONS
The 4863/2363's Digital Signals are on connector J2. Connector J2 is a 62
pin metal DC shell connector with female lockstuds that mates to a DC-62S
plug. Table 2-7 lists the J2 signal-pin assignments. Table 2-8 is a worksheet
for recording the configuration settings when designing the interface.
2.8.1 Digital I/O Overview
The digital I/O lines are controlled by 8-bit bidirectional latches. Data
direction is referred to as output when the digital lines output data received
from the GPIB or Serial bus. Data direction is input when data is read in
from the digital lines and is talked onto the GPIB bus or outputted serially.
The simplest data transfer is with the port type commands that address a
specific I/O byte or bit commands that toggle or read a specific bit. Data
polarity can be set on a bit-by-bit basis with the port commands. Bytes
controlled by the port and bit commands do not need to be configured with
the configuration commands.
String commands or transparent data strings can be used to transfer data in
multiple byte wide words. Bytes used by the string commands must be
configured into input or output strings by the configuration commands.
Depending upon the selected data format, each eight-bit byte can be
considered as two 4-bit nibbles where four bits of information are encoded
into a single character on the GPIB or serial bus. Two characters make up
a byte. Other formats let the user express a byte as decimal numbers or as
a single binary byte. Data format and polarity are the same for all configured
output or input bytes.
The 15 data lines in the first two bytes are sampled at a 1 kHz rate and their
values saved in the Questionable Register when the bytes are used as input
bytes. Changes in any of the 15 data lines can be used to generate an SRQ
or service request message. The user can select bit transition directions and
enable individual bits to detect signal changes and generate a Service
Request when an enabled bit is set. See Section 3.4 for more information
about the card's Status Reporting Structure. Bytes naturally default to
inputs and do not need to be configured with the configuration commands
to be monitored by the interface.
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