OPTO 22 AC24AT User manual

AC24AT/AC422AT
USER’S GUIDE
Form 166-040823 — August, 2004
43044 Business Park Drive, Temecula, CA 92590-3614
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AC24AT/AC422AT User’s Guide
AC24AT & AC422AT User’s Guide
Form 166-040823 — August, 2004
All rights reserved.
Printed in the United States of America.
The information in this manual has been checked carefully and is believed to be accurate; however, Opto 22 assumes no responsibility for
possible inaccuracies or omissions. Specifications are subject to change without notice.
Opto 22 warrants all of its products to be free from defects in material or workmanship for 30 months from the manufacturing date code.
This warranty is limited to the original cost of the unit only and does not cover installation, labor, or any other contingent costs. Opto 22
I/O modules and solid-state relays with date codes of 1/96 or later are guaranteed for life. This lifetime warranty excludes reed relay,
SNAP serial communication modules, SNAP PID modules, and modules that contain mechanical contacts or switches. Opto 22 does not
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applies. These products include, but are not limited to, the OptoTerminal-G70, OptoTerminal-G75, and Sony Ericsson GT-48; see the product
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AC24AT/AC422AT User’s Guide
TABLE OF CONTENTS
Chapter 1: Introduction 5
Product Description ................................................................................................... 5
Summary of Features ................................................................................................ 6
Chapter 2: Installing the Adapter Card for use with Optomux In
RS-422/485 4-wire Mode 9
Quick Start ................................................................................................................ 9
A. Checking Available Computer Resources........................................................ 9
B. Setting Jumpers for I/O Port Address and IRQ .............................................. 10
C. Setting Communication Jumpers .................................................................. 12
D. Configuring the COM Port in the Operating System ...................................... 13
E. Connecting the Adapter Card to the Optomux Network ................................. 14
Wiring Diagrams For Connecting to Classic Optomus (B1 & B2) .................. 14
Wiring Diagrams For Connecting to SNAP OptomuX (B3000)...................... 16
Chapter 3: Installing the Adapter Card for use with Devices
Other Than Optomux 19
Quick Start ........................................................................................................ 19
Chapter 4: Technical Information 21
Recommended RS-422/485 Communication Cables ............................................... 21
Communication Jumpers ......................................................................................... 22
Biasing Jumpers ............................................................................................... 22
Termination Jumpers......................................................................................... 23
Jumpers for Controlling the Transmitter on theAdapter Card ............................. 24
Other Jumpers .................................................................................................. 24
Using the AC24AT in RS-485 2-Wire Mode .............................................................. 25
Chapter 5: Troubleshooting and Testing 27
Communications Cabling......................................................................................... 27
Troubleshooting the Adapter Card with a Loop-back Connector ............................... 27
Troubleshooting Optomux Communications Using LED Indicators ........................... 29
Testing Optomux communication Through the Adapter Card Using HyperTerminal ... 30
A. HyperTerminal Installation: ............................................................................ 30
B. HyperTerminal Session Configuration: .......................................................... 30
C. Transmitting Characters to the Optomux Brain Boards .................................. 31
D. Transmitting Optomux Protocol Messages to the Optomux Brain Boards ...... 31

AC24AT/AC422AT User’s Guide
Appendix A 33
Address Jumpers (Group A Jumpers) ...................................................................... 33
Discussion ........................................................................................................ 33
Procedure......................................................................................................... 33
Appendix B 35
Application Note AN9602: Configuring the AC24AT/AC422AT as a COM Port in
Microsoft Windows 95 ............................................................................................. 35
Appendix C 37
Notes Regarding Earlier Versions of the Adapter Card ............................................. 37
Appendix D: RS-422 and RS-485 as used with
Opto 22 Products 39
General ................................................................................................................... 39
RS-422.................................................................................................................... 39
Block Diagram of RS-422 Data Link with Multiple Receivers.............................. 39
Block Diagram of RS-422 Point-to-Point Communications Link.......................... 40
Block Diagram of Classic Optomux (B1's and B2's) in Repeat Mode.................. 40
RS-485.................................................................................................................... 41
Block Diagram of RS-485 DATALink (2-Wire Mode).......................................... 41
RS-422/485............................................................................................................. 41
Block Diagram of RS-422/485 Communications Link used by
Classic Optomux (B1 & B2) in Multi-drop Mode ................................................. 42
Biasing .................................................................................................................... 43
Summary of Biasing.......................................................................................... 43
Termination ............................................................................................................. 44
Summary of Termination ................................................................................... 44
Appendix E: Glossary of Terms and Abbreviations 45
Appendix F: Product Support 47

AC24AT/AC422AT User’s Guide
INTRODUCTION
PRODUCT DESCRIPTION
The AC24AT and AC422AT cards provide an asynchronous RS-422/485 communications port for the
ISA bus. The adapter cards are seen by the computer as standard COM ports.
These cards are transient protected, feature bi-directional handshake lines for RTS and CTS, and can
drive up to 32 devices on a multi-drop network. They are designed for communicating to Optomux brain
boards in RS-422/485 4-wire mode and support baud rates up to 115.2 kbaud.
In addition, the AC24AT card provides 4,000 volts of isolation between the ISA bus and the
communications link. The AC24AT card can also be set up for RS-485 2-wire mode; however, special
software drivers are required to take advantage of this. These special software drivers are not provided
by Opto 22. For 2-wire RS-485 solutions, use Opto 22’s AC37 (ISA bus adapter) or AC7A (stand-alone
RS-232 to RS-422/485 converter).
In this manual, differences between the AC24AT and AC422AT adapter cards will be noted where these
differences apply. Unless a feature is only applicable to one specific model, the manual will use the
convention “adapter card” when referring to both models. When referring to a specific model, the
actual model number will be used.
CHAPTER 1

AC24AT/AC422AT User’s Guide
INTRODUCTION
SUMMARY OF FEATURES
• The adapter card uses the standard 16550 UART and appears as a standard COM port
to the computer
• Transient protection for RS-422/485 lines
• Multi-drop capability
• RS-422/485 balanced line drivers
• Up to 5,000 feet of cable length using shielded twisted-pair cable (Note 1)
• Data rates from 300 baud to 115.2 kbaud (Note 2)
• Bi-directional handshake lines (RTS, CTS)
• LED indicators for Transmit, Receive, RTS, and CTS
• Jumper-configurable termination and biasing for RS-422/485 lines
• Model AC24AT provides 4,000 volts of optical isolation between the computer
and the RS-422/485 lines
• Model AC24AT provides transformer isolation between the computer’s 5 VDC
and the RS-422/485 lines.
Notes: 1. At 38.4 kbaud, the distance limit is 5,000 feet.
At 115.2 kbaud, the distance limit is 3,000 feet.
2. Classic Optomux brain boards (B1 & B2) are limited to 38.4 kbaud.

AC24AT/AC422AT User’s Guide
INTRODUCTION
Figure 1-1: AC24AT (top) and AC422AT (bottom)
Revised: 12/4/98

AC24AT/AC422AT User’s Guide
INTRODUCTION

AC24AT/AC422AT User’s Guide
INSTALLING THE ADAPTER CARD
FOR USE WITH OPTOMUX IN
RS-422/485 4-WIRE MODE
QUICK START
The following steps are detailed in this chapter:
A Check available computer resources (I/O port address and IRQ) before installing the adapter
card in the computer.
B. Set jumpers for I/O port address and IRQ.
C. Set communication jumpers.
D. Configure the COM port in the operating system.
E. Connect the communications cable between the adapter card and the Optomux system.
A. CHECKING AVAILABLE COMPUTER RESOURCES
It is best to identify which I/O port addresses and IRQ settings are available on the computer before
installing the adapter card. The following tools are available to help with this:
Microsoft Windows NT: Windows NT Diagnostics can be accessed by selecting the Start button,
Programs, Administrative Tools (Common), and Windows NT Diagnostics. Once it is started, select the
Resources Tab, and then the IRQ and I/O Port buttons (one at a time).
Microsoft Windows 95: Device Manager can be accessed by selecting the Start button, Settings, and
Control Panel. Double-click on the System icon. Select the Device Manager Tab, highlight “Computer”,
and then click the Properties button. Then select the Interrupt request (IRQ) button and the Input/output
(I/O) button (one at a time).
Microsoft Windows for Workgroups: Microsoft Diagnostics (MSD) can be accessed by exiting
Microsoft Windows. From the DOS prompt (not a DOS box) type <path>MSD and press the Enter key
where <path> is the path to the Windows directory that contains the file MSD.EXE. Select the IRQ button
and the COM Ports button.
CHAPTER 2

AC24AT/AC422AT User’s Guide
ADAPTER CARD INSTALLATION
Note: These tools are a good start, but they are not foolproof. I/O port addresses and IRQ settings that are listed
as being used may or may not be available. The tools for Microsoft Windows 95 and NT typically only
reflect hardware that has been registered in the Registry. Other hardware that has not been registered
will not be reflected and may cause conflicts.
Select an I/O port address and IRQ that are available in the computer. The next section shows how to set
jumpers to configure the adapter card I/O port address and IRQ.
B. SETTING JUMPERS FOR I/O PORT ADDRESS AND IRQ
Select an available I/O port address and an available IRQ setting. Use the following tables to identify
settings for COM ports, I/O port addresses, and IRQs.
Table 2-1: Standard COM port names and corresponding I/O port addresses and IRQs.
COM Port
Name
I/O Port
Address IRQ
COM1 3F8 4
COM2 2F8 3
COM3 3E8 4
COM4 2E8 3
OPTO COM3 348 2
OPTO COM4 340 5
• A COM port in the operating system is simply a name that defines a combination of an I/O port
address and an IRQ. Whenever that COM port name is referenced, the corresponding I/O port
address and IRQ are accessed.
• COM1 and COM2 are standards for DOS and all Microsoft Windows operating systems.
• COM3 and COM4 are standards for all Microsoft Windows operating systems.
• OPTO COM3 and OPTO COM4 are Opto 22 standards that were definded prior to the release of
the Microft Windows operating systems.
• Although there are a few standard COM port settings, a COM port can be configured for any
available I/O port address and IRQ. For example, it is conceivable to set up the adapter card
as COM3 in the operating system with an I/O port address of 340 and IRQ 6. This assumes that
I/O port address 340 and IRQ 6 are not already in use on the computer, and that COM3 did not
already exist on the computer. This is an acceptable, although non-standard, setup for COM3.

AC24AT/AC422AT User’s Guide
Table 2-2: Adapter card I/O Port Address Jumpers (group A jumpers) for Standard
COM ports.
COM Port
Name
I/O Port
Address
A Jumpers
9876543
COM1 3F8
COM2 2F8 8
COM3 3E8 4
COM4 2E8 8 4
OPTO COM3 348 7 5 4
OPTO COM4 340 7 5 4 3
Notes: 1. Only install the address jumpers listed. Remove unlisted address jumpers.
2. See Appendix A for additional I/O port addresses and jumper settings.
Table 2-3: Adapter card IRQ Jumpers.
AC24AT AC422AT
COM Port
Name IRQ AC24AT IRQ
Jumper Group Notes
OPTO COM3 2 IRQ2 Notes 1, 6
N/A 7 IRQ7 Notes 1, 7
N/A 6 IRQ6 Notes 1, 7
OPTO COM4 5 IRQ5 Note 1
COM1/COM3 4 COM1 Notes 1, 4
COM2/COM4 3 COM2 Notes 1, 5
N/A CTS Note 2
N/A 2-W Note 3
COM Port
Name IRQ AC422AT IRQ Jumper Group Notes
COM2/COM4 3 COM2 Notes 1, 5
COM1/COM3 4 COM1 Notes 1, 4
OPTO COM4 5 IRQ5 Note 1
N/A 6 IRQ6 Notes 1, 7
N/A 7 IRQ7 Notes 1, 7
OPTO COM3 2 IRQ2 Notes 1, 6
N/A CTS DISABLE Note 2
Notes: 1. Only install one IRQ jumper.
2. In addition to the IRQ jumper, install the CTS/CTS DISABLE jumper.
3. Remove the 2-W jumper (AC24AT only).
4. Microsoft Windows operating systems standard is that COM1 & COM3 share the same IRQ (4).
Select a different IRQ if COM1 is being used in this computer.
5. Microsoft Windows operating systems standard is that COM2 & COM4 share the same IRQ (3).
Select a different IRQ if COM2 is being used in this computer.
6. The Microsoft Windows 95 operating system uses IRQ 2. Do not set the adapter card for IRQ 2
when using the adapter card in Windows 95.
7. IRQs 6 and 7 are also available on the adapter card.
ADAPTER CARD INSTALLATION

AC24AT/AC422AT User’s Guide
C. SETTING COMMUNICATION JUMPERS
Figures 2-1 and 2-2 show the correct jumper arrangement for all group B , group C, and CTS jumpers on
the adapter card for use with Optomux. These jumper settings are the defaults set at the factory.
Figure 2-1: AC24AT Group B and C Jumpers & CTS and 2-W Jumper Arrangements
Figure 2-2: AC422AT Group B and C Jumpers & CTS Jumper Arrangements
The adapter card is now ready to be plugged into any open ISA slot in the computer.
ADAPTER CARD INSTALLATION

AC24AT/AC422AT User’s Guide
D. CONFIGURING THE COM PORT IN THE OPERATING
SYSTEM
If the COM port does not already exist in the operating system, then it will have to be added. If it does
exist but the settings are different than the jumpers on the adapter card, then the port will have to
be modified.
Microsoft Windows NT: Select the Start button, then select Settings, and Control Panel. Double-click
on the Ports icon. Add or modify the COM port as necessary.
Microsoft Windows 95: See Appendix B for instructions.
Microsoft Windows for Workgroups: Open the Main program group, then Control Panel, and finally Ports.
Add or modify the COM port as necessary.
Microsoft DOS: The COM port is simply accessed by the application software using the appropriate
I/O port and IRQ settings.
The adapter card is seen by the computer’s operating system as a standard COM port. It uses the
standard operating system API drivers, so special software drivers are not needed.
The adapter card is not plug-and-play compatible. If the computer has the plug-and-play feature turned
on in the computer’s BIOS, then it must be turned off.
If the computer has COM1 and/or COM2 ports built into the mother board, then it will not be possible
to configure the adapter card with the same COM port settings without disabling the computer’s built-in
COM port. The computer’s built-in COM port must first be disabled by changing the enable status of the
COM port in the computer’s BIOS. A computer’s BIOS settings can typically only be accessed during the
initial boot sequence when starting or restarting the computer.
ADAPTER CARD INSTALLATION

AC24AT/AC422AT User’s Guide
E. CONNECTING THE ADAPTER CARD TO THE
OPTOMUX NETWORK
For this connection, Opto 22 recommends that a cable with three or four twisted pairs and an overall
shield be used. This will provide a total of 6 or 8 wires in addition to the shield drain wire. All conductors
should be stranded #22 or #24 gauge, with a nominal impedance of 100 ohms and a capacitance of
12.5 pF/ft. See Chapter 4, Technical Information, Recommended RS-422/485 Communication Cables.
Notes: AC24AT: Signal common is NOT tied to the computer’s ground and should NOT be tied to earth ground at
any location.
AC422AT: Signal common is tied to the computer’s ground and should NOT be tied to earth ground at any
other location.
Wiring Diagrams For Connecting to Classic OptomuX (B1 & B2)
Standard Configuration
This Standard Configuration is highly recommended and provides the best noise immunity.
The first pair of twisted wire connects the TO+ and TO- terminals on the adapter card to the FH+ and
FH- terminals on the Optomux unit (TO+ to FH+ and TO- to FH-). The second pair of twisted wire connects
the FO+ and FO- terminals on the adapter card to the TH+ and TH- terminals on the Optomux unit. One
wire from the third pair of twisted wire connects the LOGIC GND terminal on the adapter card to the
COM terminal of the Optomux unit. Finally, the overall cable shield drain wire should be tied to earth
ground at only one of its two ends.
Figure 2-3: RS-422/485 Wiring from Adapter Card to Classic Optomux Brain Board (B1 or B2)
ADAPTER CARD INSTALLATION

AC24AT/AC422AT User’s Guide
Alternate Configuration
This Alternate Configuration uses a cable with only two twisted pairs and an overall shield and is
acceptable in most cases. However, it provides less noise immunity because the shield is not used as
a shield; it is used as a convenient extra wire for the logic common for the network.
The first pair of twisted wire connects the TO+ and TO- terminals on the adapter card to the FH+
and FH- terminals on the Optomux unit (TO+ to FH+ and TO- to FH-). The second pair of twisted wire
connects the FO+ and FO- terminals on the adapter card to the TH+ and TH- terminals on the Optomux
unit.
The overall cable shield drain wire connects the LOGIC GND terminal on the adapter card to the
COM terminal of the Optomux unit.
Figure 2-4: RS-422/485 Wiring from Adapter Card to Classic Optomux Brain Board
(B1 or B2)
The overall cable shield drain wire should NOT be tied to earth ground at any location because it is being
used as the logic common for the network.
For details on connecting multiple Optomux brain boards to the RS-422/485 communication
cable, please see the
Optomux B1 and B2 Data Sheet (form 463).
ADAPTER CARD INSTALLATION

AC24AT/AC422AT User’s Guide
Wiring Diagrams For Connecting to SNAP OptomuX (B3000)
Standard Configuration
This Standard Configuration is highly recommended and provides the best noise immunity.
The first pair of twisted wire connects the TX+ and TX- terminals on the adapter card to the RX+
and RX- terminals on the Optomux unit (TX+ to RX+ and TX- to RX-). The second pair of twisted wire
connects the RX+ and RX- terminals on the adapter card to the TX/RX+ and TX/RX- terminals on the
Optomux unit. One wire from the third pair of twisted wire connects the LOGIC GND terminal on the
adapter card to the COM terminal of the Optomux unit. Finally, the overall cable shield drain wire
should be tied to earth ground at only one of its two ends.
Figure 2-5: RS-422/485 Wiring from Adapter Card to Optomux SNAP B3000 Brain
ADAPTER CARD INSTALLATION

AC24AT/AC422AT User’s Guide
Alternate Configuration
This Alternate Configuration uses a cable with only two twisted pairs and an overall shield and is
acceptable in most cases. However, it provides less noise immunity because the shield is not used as
a shield; it is used as a convenient extra wire for the logic common for the network.
The first pair of twisted wire connects the TX+ and TX- terminals on the adapter card to the RX+ and RX-
terminals on the Optomux unit (TX+ to RX+ and TX- to RX-). The second pair of twisted wire connects the
RX+ and RX- terminals on the adapter card to the TX+ and TX- terminals on the Optomux unit.
The overall cable shield drain wire connects the LOGIC GND terminal on the adapter card to the
COM terminal of the Optomux unit.
Figure 2-6: RS-422/485 Wiring from Adapter Card to Optomux SNAP B3000 Brain
The overall cable shield drain wire should NOT be tied to earth ground at any location because it is being
used as the logic common for the network.
For details on connecting multiple Optomux brain boards to the RS-422/485 communication
cable, please see the B3000 data sheet (form 787).
ADAPTER CARD INSTALLATION

AC24AT/AC422AT User’s Guide
ADAPTER CARD INSTALLATION

AC24AT/AC422AT User’s Guide
INSTALLING THE ADAPTER CARD
FOR USE WITH DEVICES
OTHER THAN OPTOMUX
QUICK START
A. Check available computer resources (I/O port address and IRQ) before installing the
adapter card in the computer. See Chapter 2, Step A.
B. Set jumpers for I/O port address (group A jumpers) and IRQ. See Chapter 2, Step B.
C. Set communication jumpers (group B & C jumpers as well as the CTS DISABLE and
2-W jumpers). See “Communication Jumpers” Section of Chapter 4.
D. Configure the COM port in the operating system. See Chapter 2, Step D.
E. Connect the communications cable between the adapter card and the Rs-422 or RS-485 device.
The following diagram shows the connection between the adapter card and another RS-422/485
device. Please note that the transmit lines from the adapter card must be connected to the receive
lines of the terminal or computer, and vice versa. See the section titled, “Communication Jumpers (Group
B & C Jumpers + CTS-Disable and 2-W Jumpers)” earlier in this chapter for instructions on setting
communication jumpers.
CHAPTER 3

AC24AT/AC422AT User’s Guide
ADAPTER CARD INSTALLATION (cont.)
Figure 3-1: Connection between the adapter card and another RS-422/485 device.
Figure 3-2: J1 9-Pin D Shell (female) Connector
When communicating via RS-422 or RS-485 to other non-Opto 22 devices, termination provisions may
not be available on the devices. It may be necessary to install 220 ohm terminating resistors at, but
external to, the device.