INTERFACES
TRADITIONAL
PC ADAPTER CARDS
Form 473-010131
DATA SHEET
page 1/6
Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: (951) 695-3000 • (800) 321-OPTO • Fax: (951) 695-3095 • www.opto22.com
Inside Sales: (800) 321-OPTO • Product Support: (800) TEK-OPTO • (951) 695-3080 • Fax: (951) 695-3017 • E-mail: sales@opto22.com
The AC422AT is a non-isolated RS-422/485 adapter card that plugs directly into the IBM PC bus. The AC422AT is transient-
protected, features bi-directional handshake lines for RTS and CTS, and can drive up to 100 devices on a multidrop network. The
AC422AT can be jumpered for operation as COM1, COM2, COM3, or COM4 and offers full hardware and software compatibility
with IBM PC, XT, and compatible computers.
Description
Part
Number Descrption
AC422AT ISA Bus Serial Port RS422/485, Non-Isolated
INTERFACES
TRADITIONAL
PC ADAPTER CARDS
Form 473-010131
DATA SHEET
page 2/6
Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: (951) 695-3000 • (800) 321-OPTO • Fax: (951) 695-3095 • www.opto22.com
Inside Sales: (800) 321-OPTO • Product Support: (800) TEK-OPTO • (951) 695-3080 • Fax: (951) 695-3017 • E-mail: sales@opto22.com
Dimension and specifications are subject to change. All products and/or company names throughout this data sheet are generally trademarks or registered trademarks of their respective companies.
Interface Specifications
GENERAL
Specifications
Dimensional Drawing
Power Requirements
250 mA at 5 VDC
150 mA at 12 VDC
150 mA at 12 VDC
Operating
Temperature Range
0° C to 60° C
95% relative humidity, non-condensing
Interface RS-422/485 (9-pin, D-shell female connector)
Baud Rate up to 38,400 baud
Distance up to 5,000 feet
Communications full duplex over two twisted pairs and a ground
additional twisted pairs for RTS and CTS
Indicators transmit, receive, RTS, and CTS
INTERFACES
TRADITIONAL
PC ADAPTER CARDS
Form 473-010131
DATA SHEET
page 3/6
Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: (951) 695-3000 • (800) 321-OPTO • Fax: (951) 695-3095 • www.opto22.com
Inside Sales: (800) 321-OPTO • Product Support: (800) TEK-OPTO • (951) 695-3080 • Fax: (951) 695-3017 • E-mail: sales@opto22.com
Jumper Installation
CONFIGURING FOR THE AC422AT
Before installing your adapter card, configure your board by selecting the appropriate address, interrupt, and communications jumpers.
These adapter cards can be configured as COM1 through COM4. Select which COM port is to be used based on the current
configurations of the COM ports in the host PC. Refer to the following diagrams for jumper settings for the various COM ports.
COMPATIBILITY
The AC422AT use the same UART used in the AT model computers.
The RS-422/485 adapter cards are seen by the computer as a standard serial port and will pass the IBM Advanced Diagnostics program
if a loop-back connector is used.
AC24AT
and
AC422AT
Address IRQ
Group A
Jumpers
Installed
IRQ
Jumpers
COM1 3F8 Hex 4 NONE COM1
COM2 2F8 Hex 3 8 COM2
COM3 348 Hex 2 4, 5, 7 IRQ2
COM4 340 Hex 5 3, 4, 5, 7 IRA5
INTERFACES
TRADITIONAL
PC ADAPTER CARDS
Form 473-010131
DATA SHEET
page 4/6
Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: (951) 695-3000 • (800) 321-OPTO • Fax: (951) 695-3095 • www.opto22.com
Inside Sales: (800) 321-OPTO • Product Support: (800) TEK-OPTO • (951) 695-3080 • Fax: (951) 695-3017 • E-mail: sales@opto22.com
Jumper Installation (cont.)
COMMUNICATION JUMPERS
Installing jumpers B2 and B4 connects 220 ohm terminating resistors from positive (+) to negative (-) on the transmitter (to Optomux)
and receiver (from Optomux), respectively. In a normal OPTOMUX network these jumpers should both be installed.
Installing jumpers C2 and C4 connects 200 ohm terminating resistors for positive (+) to negative (-) on the RTS and CTS, respectively.
In a normal network these jumpers should both be installed.
Note: If multiple host computers are used, jumpers B2, B4, C2, and C4 should only be installed on the adapter card which is physically at the end of the serial network
cable.
Jumper B7 controls the enabling of the RS-422/485 driver. With the jumper removed, the driver is always enabled. With the jumper
installed, the enabling is under the control of the RTS output on the UART. When the RTS is active, the driver will be enabled. When RTS
is inactive, the driver is disabled.
If jumper B7 is installed, jumpers B1 and B3 must also be installed. These jumpers passively pull the transmit lines (to OPTOMUX) to
the inactive state.
If the adapter card is operating with a multidrop OPTOMUX network, jumpers B5 and B6 must be installed. These jumpers passively
pull the receive (from OPTOMUX) to the inactive state. Also, C5 and C6 must be installed to passively pull the CTS to the inactive state.
Jumper C7 controls the enabling of the RS-422/485 driver. With the jumper installed, the enabling is under the control of the CTS input
from the RS-422/485 connection. Jumpers B7 and C7 should never be installed at the same time.
The CTS jumper should always be installed on the adapter card when the RTS/CTS handshake lines are NOT being used. With earlier
revision adapter cards which do not hae a CTS jumper, the RTS outputs must be looped back to the CTS inputs. This is done by connecting
the RTS positive (+) pin to the CTS positive (+) pin, and the RTS negative (-) pin to the CTS negative (-) pin using a suitable jumper wire
soldered on the 9-pin connector on the adapter end of the cable.
The 2-wire jumper switches the card from 4-wire to 2-wire mode. A jumper out, which is the factory default, sets the card into 4-wire
mode. A jumper installed sets the card into 2-wire mode.
INTERFACES
TRADITIONAL
PC ADAPTER CARDS
Form 473-010131
DATA SHEET
page 5/6
Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: (951) 695-3000 • (800) 321-OPTO • Fax: (951) 695-3095 • www.opto22.com
Inside Sales: (800) 321-OPTO • Product Support: (800) TEK-OPTO • (951) 695-3080 • Fax: (951) 695-3017 • E-mail: sales@opto22.com
Jumper Installation (cont.)
ADDRESS JUMPERS
On the RS-422/485 adapter card, there are seven jumpers labeled A3 through A9. These jumpers are used for selecting the base
address of the adapter card.
The IBM personal computers only use 10 address lines (A0 through A9) for addressing I/O boards. The UART chip on the adapter card
uses the lower three address lines (A0 through A2) directly. This leaves seven address lines (A3 through A9) for decoding the base address
of the adapter card.
The adapter card compares the address lines A3 through A9 on the bus with the address jumpers A3 through A9. When the address
lines match the jumper lines, the adapter card is selected.
When a jumper is present, the jumper value is low (zero). When a jumper is not present, the jumper value is high (one).
With no address jumpers present, the adapter card will be selected from address 3F8 to 3FF hex (addressed as COM1).
You can set the adapter card for a particular base address as follows:
First, write the desired base address as a three-digit, hexadecimal number. The number must be less than 3FF and have a zero
or an eight as the last digit. Also, the number must be chosen so as not to conflict with the base address of any other installed
cards in the computer.
Second, translate the number to binary and discard the first two zeros and the last three zeros.
Finally, install a jumper in each location corresponding to a zero. The most significant bit corresponds to A9, and the least
significant to A3. For example:
Install jumpers at A8, remove A3 through A7, and A9.
Note: If you address the adapter card for an address other than COM1 or COM2, you will need to provide your own interface and initialization routines. The IBM PC or
PC/AT Technical Reference Manual has a good section on the operation f the UART and a listing of the code used in the BIOS to access the communications ports.
Address Binary Discard
Ends
2 0010 10
F 1111 1111
810 1
INTERFACES
TRADITIONAL
PC ADAPTER CARDS
Form 473-010131
DATA SHEET
page 6/6
Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: (951) 695-3000 • (800) 321-OPTO • Fax: (951) 695-3095 • www.opto22.com
Inside Sales: (800) 321-OPTO • Product Support: (800) TEK-OPTO • (951) 695-3080 • Fax: (951) 695-3017 • E-mail: sales@opto22.com
Jumper Installation (cont.)
INTERRUPT JUMPERS
If you need to select a specific interrupt line for your software, jumpers for interrupt request lines IRQ2 and IRQ5 through IRQ7 are
provided in addition to the COM1 (IRQ4) and COM2 (IRQ3) jumpers. IBM PC BASIC uses interrupt driven communications, and therefore
requires that the COM1 (or COM2) interrupt jumpers be installed when doing communications using COM1 (or COM2) from BASIC.
GROUP B AND C JUMPERS
The tables below show the normal jumper arrangement for jumper positions B1 through B8 and C1 through C7. This arrangement is
suitable if the adaper card is being used to communicate with an OPTOMUX network. For other possible configurations, refer to figure 1.
Group B Jumpers
Group C Jumpers
X = Jumper Installed
: = Jumper not Installed
FIGURE 1 - GROUP B AND C JUMPER SCHEMATIC
:X :XXX : :
12345678
:X :XXX :
1234567
© 1991–2001 Opto 22. All rights reserved. All trademarks, trade names, logos, and service marks referenced herein belong to their respective companies.
INTERFACES
TRADITIONAL
PC ADAPTER CARDS
Form 473-010131
DATA SHEET
page 7/6
Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: (951) 695-3000 • (800) 321-OPTO • Fax: (951) 695-3095 • www.opto22.com
Inside Sales: (800) 321-OPTO • Product Support: (800) TEK-OPTO • (951) 695-3080 • Fax: (951) 695-3017 • E-mail: sales@opto22.com
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Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: (951) 695-3000 • (800) 321-OPTO • Fax: (951) 695-3095 • www.opto22.com
Inside Sales: (800) 321-OPTO • Product Support: (800) TEK-OPTO • (951) 695-3080 • Fax: (951) 695-3017 • Email: sales@opto22.com • Form 1335-050601
© 2004-2005 Opto 22. All rights reserved. All trademarks, trade names, logos, and service marks referenced herein belong to their respective companies.
