MicroChannel Adapter Database
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Entry updated Jan 2007
 6C68 ::: Opto 22 Dual RS-485 Serial Port
 Original image courtesy of David Ress, 2007.

Adapter ID

Adapter ID
Opto 22 Dual RS-485 Serial Port
COM SER  Serial Port


Text and information on this page have been kindly contributed by David Ress (Jan 2007).

The AC32 is a dual RS-422/485 adapter card which plugs into the IBM PS/2 MicroChannel bus. The AC32 is transient protected and features two independent asynchronous channels (each able to drive up to 100 devices on a multi-drop network.) Channel A can be selected for COM1 through COM8 and channel B may be selected for COM2 through COM8. The AC32 offers full hardware and software compatibility with IBM PS/2 and compatible computers.

RS-422/485 line drivers are used to give the AC32 asynchronous adapter card the ability to communicate over long distances (5,000 feet) at baud rates up to 38.4k baud using two twisted parts per channel and a ground. The RS-422/485 drivers are highly immune to electrical noise.

The four LEDs on the card (cf. outline above) monitor the transmit and receiving of data on the two ports.

Each port is configured on the adapter by a group of 8 jumpers. For each port, the following table defines the jumpers for each port. Default jumper settings are shown when the board is used in an Optomux network.

PinDefaultPort A and Port B
1OFFPULL UP for the transmit line
2ONTERMINATE for the transmit line
3OFFPULL DOWN for the transmit line
4ONTERMINATE for the receive line
5ONPULL DOWN for the receive line
6ONPULL UP for the receive line
7OFFEnable RS-422/485 driver from the RTS output on the UART


The operating system should automatically find and use the RS-422/482 ports as serial ports. However, it may be necessary to add them to the operating system such as with the Ports applet in the Control Panel under NT 4.0. They are accessed via programs as the COM-number specified in the ADF, i.e. COM2, COM3, etc.


The Opto22 site at www.opto22.com maintains downloads for the Optomux software and documentation. Search in the Opto22 site through the support section on Optomux. The manual for the AC32 is available at contacting the Opto22 support staff, they will fax and/or mail it to you.

To learn more about Optomux and the various MCA and non-MCA accessories Opto22 produces, see the 0524_Optomux_Data_Book.pdf dated Oct 2, 2000. This manual discusses the Optomux protocol and its accessories.

ADF Adapter Description File


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