Measurement Computing CIO-DUAL422 - Manual

DS cio-com_dual422_com485.docx
Document Revision 2, September, 2009
Copyright © Measurement Computing Corporation
CIO-COM422, CIO-DUAL422, and CIO-COM485 Installation Guide
Standard 9-pin and 25-pin connectors
The CIO-COM422 combines an RS232 and
an RS422 interface with a single
communications port. RS232 is commonly a
25-pin connector, while RS422 is a 9-pin
connector.
The pin assignments shown here conform to
the RS232 and RS422 standards.
The CIO-DUAL422 combines a pair of
communications ports each with RS422
standard interfaces. Each COM port uses one
of the 9-pin connectors shown here. The CIO-COM485 is equipped with two DB9
connectors for RS485 standard 9-pin connectors
and cables. The RS485 standard allows multiple
transmitters and receivers on a single
communications cable.
The CIO-COM485 facilitates interconnection
by providing two connectors wired in parallel to
the single communications port. In this manner,
standard cables may be used without a "T".
Base Address
Personal computer COM1, 2, 3, or 4 ports are assigned through a
combination of base address and interrupt level. Each COM board has
one base address switch for each COM chip.
To operate correctly with personal computer COM# software drivers,
the guidelines for both address and interrupt level should be adhered to.
CIO-COM422 Protocol Select switch
There are 5 possible protocol selections available through the protocol
select switch:
 Standard RS232 with
RTS, DTR, and CTS.
 RS232 without RTS,
DTR, and CTS.
 Current loop.
 RS422 with RTS and
CTS control signals.
 RS422 without RTS
and CTS.
Interrupt Level jumper
Communications software such as the standard COM drivers included
with DOS and Windows use interrupt service routines assigned to
specific interrupt numbers. Choose the correct interrupt number by
setting the jumper on
the CIO-COM board.
Different computers
require different
interrupt settings for
COM3: and COM4:.
Check with your PC
owner's manual for the
correct IRQ settings on
your computer.
CIO-DUAL422 CTS/RTS Enable jumper
RS422 may be used with or
without hardware handshaking.
The Clear To Send (CTS) and
RTS signal lines may be enabled
or disabled by setting a jumper
on the CIO-DUAL422.