44474A 16-Bit Digital I/O Module - Agilent Technologies Agilent 3499A User Manual

7
Chapter 7 Plug-in Modules

44474A 16-Bit Digital I/O Module

44474A 16-Bit Digital I/O Module
The Agilent 44474A Digital I/O module provides 16 bidirectional data
lines (bits) plus 4 lines used for control and handshaking. All lines are
TTL compatible. The 16 I/O lines or bits can be addressed individually
(bit-by-bit), as two independent 8-bit ports, or as one 16-bit word.
The two 8-bit ports are completely independent of each other and may be
used separately. For instance, one port can be used for output operations,
while the other for input. However, all 8 bits in a given port must be
either input or output bits (not a combination of input and output).
Five handshaking modes are available for this module. The handshaking
modes are described beginning on page 98. Handshaking uses up to
three control lines:
•
Peripheral Control (PCTL)
•
I/O direction (I/O)
•
Peripheral Flag (PFLG or EI)
Additionally, the 44474A provides an additional Channel Closed (CC)
line that changes state to indicate a channel has been closed. The
External Increment (EI) and Channel Closed (CC) lines can be used to
control an external instrument such as a DMM. For example, Agilent
DMMs have a Voltmeter Complete line that indicates when a
measurement has completed. This line is connected to the 44474A EI
input and the Channel Closed output is connected to the DMM External
Trigger. When properly configured, a scan list can then be executed and
measured without external computer control.
Port and bit numbering is show in the table below. Note that the ports
are numbered differently if you are using the 3488 System mode.
System Mode 16-Bit Port #
SCPI mode PORT 00
3488A Mode PORT 02
Specifications for the 44474A are given on page 341.
248
8-Bit Port # Bit #
PORT 00 Bits 0-7 (LO BYTE)
PORT 01 Bits 0-7 (HI BYTE)
PORT 00 Bits 0-7 (LO BYTE)
PORT 01 Bits 0-7 (HI BYTE)