Black Box Network Card IC133C R2 User Manual

AUGUST 2000  
IC133C-R2  
IC187C  
2-Port RS-232/422/485  
PCI Host Adapter  
CUSTOMER  
SUPPORT  
INFORMATION  
Order toll-free in the U.S. 24 hours, 7 A.M. Monday to midnight Friday: 877-877-BBOX  
FREE technical support, 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746  
Mail order: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
EUROPEAN UNION DECLARATION OF CONFORMITY  
Products bearing the CE Label fulfill the requirements of the EMC directive  
(89/336/EEC) and of the low-voltage directive (73/23/EEC) issued by the  
European Commission.  
To obey these directives, the following European standards must be met:  
• EN55022 Class A - “Limits and methods of measurement of radio interference  
characteristics of information technology equipment”  
• EN50082-1 - “Electromagnetic compatibility - Generic immunity standard”  
Part 1: Residential, commercial and light industry  
• EN60950 (IEC950) - “Safety of information technology equipment, including  
electrical business equipment”  
Use high quality shielded cabling with this product to maintain compliance with  
the EMC directive.  
2
 
NOM STATEMENT  
NORMAS OFICIALES MEXICANAS (NOM)  
ELECTRICAL SAFETY STATEMENT  
INSTRUCCIONES DE SEGURIDAD  
1. Todas las instrucciones de seguridad y operación deberán ser leídas antes  
de que el aparato eléctrico sea operado.  
2. Las instrucciones de seguridad y operación deberán ser guardadas para  
referencia futura.  
3. Todas las advertencias en el aparato eléctrico y en sus instrucciones  
de operación deben ser respetadas.  
4. Todas las instrucciones de operación y uso deben ser seguidas.  
5. El aparato eléctrico no deberá ser usado cerca del agua—por ejemplo,  
cerca de la tina de baño, lavabo, sótano mojado o cerca de una alberca, etc.  
6. El aparato eléctrico debe ser usado únicamente con carritos o pedestales que  
sean recomendados por el fabricante.  
7. El aparato eléctrico debe ser montado a la pared o al techo sólo como sea  
recomendado por el fabricante.  
8. Servicio—El usuario no debe intentar dar servicio al equipo eléctrico más allá  
a lo descrito en las instrucciones de operación. Todo otro servicio deberá ser  
referido a personal de servicio calificado.  
9. El aparato eléctrico debe ser situado de tal manera que su posición no  
interfiera su uso. La colocación del aparato eléctrico sobre una cama, sofá,  
alfombra o superficie similar puede bloquea la ventilación, no se debe  
colocar en libreros o gabinetes que impidan el flujo de aire por los orificios  
de ventilación.  
10. El equipo eléctrico deber ser situado fuera del alcance de fuentes de calor  
como radiadores, registros de calor, estufas u otros aparatos (incluyendo  
amplificadores) que producen calor.  
11. El aparato eléctrico deberá ser connectado a una fuente de poder sólo del  
tipo descrito en el instructivo de operación, o como se indique en el aparato.  
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2-PORT RS-232/422/485 PCI HOST ADAPTER  
12. Precaución debe ser tomada de tal manera que la tierra fisica y la polarización  
del equipo no sea eliminada.  
13. Los cables de la fuente de poder deben ser guiados de tal manera que  
no sean pisados ni pellizcados por objetos colocados sobre o contra ellos,  
poniendo particular atención a los contactos y receptáculos donde salen  
del aparato.  
14. El equipo eléctrico debe ser limpiado únicamente de acuerdo a las  
recomendaciones del fabricante.  
15. En caso de existir, una antena externa deberá ser localizada lejos  
de las lineas de energia.  
16. El cable de corriente deberá ser desconectado del cuando el equipo  
no sea usado por un largo periodo de tiempo.  
17. Cuidado debe ser tomado de tal manera que objectos liquidos no sean  
derramados sobre la cubierta u orificios de ventilación.  
18. Servicio por personal calificado deberá ser provisto cuando:  
A: El cable de poder o el contacto ha sido dañado; u  
B: Objectos han caído o líquido ha sido derramado dentro del aparato; o  
C: El aparato ha sido expuesto a la lluvia; o  
D: El aparato parece no operar normalmente o muestra un cambio  
en su desempeño; o  
E: El aparato ha sido tirado o su cubierta ha sido dañada.  
TRADEMARKS  
The trademarks mentioned in this manual are acknowledged to be the property of the  
trademark owners.  
4
 
TABLE OF CONTENTS  
CONTENTS  
1. Specifications............................................................................................7  
2. Introduction.............................................................................................8  
2.1 Overview .............................................................................................8  
2.2 What’s Included.................................................................................8  
2.3 Factory Default Settings.....................................................................9  
3. Card Setup................................................................................................10  
3.1 RS-485 Enable Modes ........................................................................10  
3.2 Address and IRQ Selection ...............................................................12  
3.3 Line Termination...............................................................................12  
3.4 Electrical Interface Selection............................................................14  
3.5 Clock Modes.......................................................................................15  
3.6 Baud Rates and Divisors for the “Div 1” Mode ................................16  
3.7 Baud Rates and Divisors for the “Div 2” Mode ................................18  
4. Installation................................................................................................20  
4.1 Setting Up the Operating System.....................................................20  
4.1.1 Windows 3.1x ...........................................................................20  
4.1.2 Windows 95/98 ........................................................................20  
4.1.3 Windows NT.............................................................................21  
4.1.4 DOS...........................................................................................21  
4.1.5 Other Operating Systems........................................................21  
4.2 Installing the Hardware.....................................................................21  
5. Troubleshooting ......................................................................................22  
5.1 The Serial Utility Diskette ................................................................22  
5.2 Calling Black Box..............................................................................23  
5.3 Shipping and Packaging...................................................................23  
Appendix A: Interrupt Handling ...............................................................24  
A.1 The Purpose and Early History of Interrupts..................................24  
A.2 Why Use an ISP?................................................................................25  
Appendix B: Connector Pinouts ................................................................26  
B.1 RS-232.................................................................................................26  
B.2 RS-422/485 ........................................................................................27  
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2-PORT RS-232/422/485 PCI HOST ADAPTER  
CONTENTS (continued)  
Appendix C: Electrical Interfaces...............................................................28  
C.1 RS-232.................................................................................................28  
C.2 RS-422.................................................................................................28  
C.3 RS-485.................................................................................................29  
Appendix D: Asynchronous Communications..........................................30  
Appendix E: Board Layout..........................................................................32  
6
 
CHAPTER 1: Specificatiobns  
1. Specifications  
Communication Chip — IC133C-R2: 16550 UART (optionally, you can  
remove this UART and install a 16950 UART for better performance);  
IC187C: 16950 UART  
Data Rate — IC133C-R2: Up to 460.8 kbps; IC187C: 460.8 kbps and above  
Distance — Up to 4000 ft. (1219.2 m)  
Number of Ports — (2) RS-232/422/485  
Connectors — (2) DB9 male  
Temperature — Operating: 32 to 122°F (0 to 50°C); Storage: -4 to +158°F  
(-20 to +70°C)  
Relative Humidity — 10 to 90%, noncondensing  
MTBF — Greater than 150,000 hours  
Power — +12 VDC @ 50 mA, -12 VDC @ 50 mA, +5 VDC @ 480 mA  
Size — 4.2"H x 5"L (10.7 x 12.7 cm)  
Weight — 1.3 lb. (0.6 kg)  
7
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
2. Introduction  
2.1 Overview  
The 2-Port RS-232/422/485 PCI Host Adapter is a two-channel PCI-bus serial I/O  
adapter for PCs and compatibles that supports data rates up to 460.8 kbps. It has  
two very versatile asynchronous serial ports: They are field-selectable as either  
RS-232 ports (suitable for communication with modems, printers and plotters) or  
RS-422/485 ports (suitable for industrial automation and control applications).  
Configure both of the Adapter’s ports as RS-232 for standard serial COM-port  
requirements. Choose the RS-422 mode for long-distance device connections up to  
4000 ft. (1219.2 m) where noise immunity and high data integrity are essential.  
Select RS-485 and capture data from multiple peripherals in a RS-485 multidrop  
network. Up to 31 RS-485 devices can be connected to each port to automate your  
data collection. You can even mix the ports in any of the interface combinations to  
provide maximum flexibility to your application.  
In both RS-232 and RS-422 modes, the card works seamlessly with the standard  
operating-system serial driver. In RS-485 mode, our special auto-enable feature  
allows the RS-485 ports to be viewed by the operating system as a COM port. This  
allows the standard COM driver to be used for RS-485 communications. The on-  
board hardware automatically handles the RS-485 driver enable.  
The IC133C-R2 adapter uses a 16550 UART. This chip features programmable  
baud rates, data format, interrupt control and a 16-byte input and output FIFO.  
You can replace the 16550 with a 16950 UART for even better performance. The  
IC187C comes with the 16950 UART already installed.  
2.2 What’s Included  
The Adapter is shipped with the following items. If any of these items are missing  
or damaged, contact the supplier.  
• (1) 2-Port RS-232/422/485 Serial Host Adapter  
• (2) 3.5” Serial Utility Diskettes  
• This User Manual  
8
 
CHAPTER2: Introduction  
2.3 Factory Default Settings  
The Adapter’s factory-default settings are as follows:  
Table 2-1. Factory-Default Settings  
Port #  
Port 1  
Port 2  
Electrical Specification  
RS-232  
RS-232  
For your reference, record installed Adapter settings below.  
Table 2-2. Installed Adapter Settings  
Port #  
Port 1  
Port 2  
Electrical Specification  
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2-PORT RS-232/422/485 PCI HOST ADAPTER  
3. Card Setup  
NOTE  
In all cases J1x refers to settings for the first port and J2x refer  
to settings for the second port.  
3.1 RS-485 Enable Modes  
RS-485 is ideal for multidrop or network environments. RS-485 requires a tri-state  
driver that will allow the electrical presence of the driver to be removed from the  
line. The driver is in a tri-state or high-impedance condition when this occurs.  
Only one driver may be active at a time, and the other driver(s) must be tri-stated.  
The output modem control signal Request To Send (RTS) is typically used to  
control the state of the driver. Some communication-software packages refer to  
RS-485 as RTS enable or RTS block mode transfer.  
One of the unique features of the Adapter is the ability to be RS-485 compatible  
without the need for special software or drivers. This ability is especially useful in  
Windows, Windows NT, and OS/2 environments, where the lower-level I/O  
control is abstracted from the application program. This ability means that the user  
can effectively use the Adapter in a RS-485 application with existing (i.e. standard  
RS-232) software drivers.  
Headers J1B and J2B are used to control the RS-485 mode functions for the  
driver circuit. The selections are “RTS” enable (marked “RT”) or “Auto” enable  
(marked “AT”). The “Auto” enable feature automatically enables/disables the  
RS-485 interface. The “RTS” mode uses the “RTS” modem-control signal to enable  
the RS-485 interface and provides backward compatibility with existing software  
products.  
Position 3 (marked “NE”) of J1B and J2B is used to control the RS-485  
enable/disable functions for the receiver circuit and determine the state of the  
RS-422/485 driver. The RS-485 “Echo” is the result of connecting the receiver  
inputs to the transmitter outputs. Every time a character is transmitted, it is also  
received. This can be beneficial if the software can handle echoing (i.e. using  
received characters to throttle the transmitter) or it can confuse the system if the  
software does not. To select the “No Echo” mode, select the position marked “NE.”  
For RS422/530/449 compatibility, remove the jumpers at J1B and J2B.  
10  
 
CHAPTER 3: Card Setup  
Examples on the following pages describe all of the valid settings for J1B  
and J2B.  
Interface Mode Examples J1D – J4D  
AT  
RT  
NE  
Figure 3-1. Headers J1B and J2B set for RS-422.  
AT  
RT  
NE  
Figure 3-2. Headers J1B and J2B set for RS-485 “Auto” with “No Echo.”  
AT  
RT  
NE  
Figure 3-3. Headers J1B and J2B set for RS-485 “Auto” with “Echo.”  
11  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
AT  
RT  
NE  
Figure 3-4. Headers J1B and J2B set for RS-485 “RTS” with “No Echo.”  
AT  
RT  
NE  
Figure 3-5. Headers J1B and J2B set for RS-485 “RTS” with “Echo.”  
3.2 Address and IRQ selection  
The Adapter is automatically assigned I/O addresses and IRQs by your  
motherboard BIOS. Only the I/O address may be modified by the user.  
Adding or removing other hardware may change the assignment of I/O  
addresses and IRQs.  
3.3 Line Termination  
Typically, each end of the RS-485 bus must have line terminating resistors  
(RS-422 terminates at the receive end only). A 120-ohm resistor is across each  
RS-530/422/485 input in addition to a 1K ohm pull-up/pull-down combination  
that biases the receiver inputs. Headers J1A and J2A allow the user to customize  
this interface to their specific requirements. Each jumper position corresponds to  
a specific portion of the interface. If multiple Adapters are configured in a RS-485  
network, only the boards on each end should have jumpers T, P & P ON. Refer to  
the following table for each position’s operation:  
12  
 
CHAPTER 3: Card Setup  
Table 3-1. Jumper Operation  
Name  
Function  
P
Adds or removes the 1K-ohm pull-down resistor in the  
RS-422/RS-485 receiver circuit (Receive data only).  
T
L
L
Adds or removes the 120-ohm termination.  
Connects the TX+ to RX+ for RS-485 two-wire operation.  
Connects the TX- to RX- for RS-485 two-wire operation.  
P
P
T
L
L
Figure 3-6. Headers J1A and J2A, which control line termination.  
13  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
3.4 Electrical Interface Selection  
Each port on the Adapter has the ability to be used in either RS-232 or  
RS-422/485 mode. This is selectable via four 24 pin DIP-shunts at E1-E4. Please  
use the following illustration to aid in the configuration of your electrical interface.  
E1  
E2  
E3  
E4  
RS-232  
RS-422/485  
E1  
E2  
E3  
E4  
RS-232 and RS-422/485  
Figure 3-7. Headers E1 through E4, which control electrical-interface  
selection.  
14  
 
CHAPTER 3: Card Setup  
3.5 Clock Modes  
The Adapter employs a clocking option that allows you to select from “divide by 4,”  
“divide by 2,” and “divide by 1” clocking modes. These modes are selected at  
Headers J1C through J4C.  
To select the baud rates commonly associated with COM ports (for example,  
2400, 4800, 9600, and 19,200 bps, and so on up to 115.2 kbps), place the jumper in  
the “divide by 4” mode (marked DIV4).  
DIV1  
DIV2  
DIV4  
Figure 3-8. Clocking mode “divide by 4.”  
To double these rates, so that the Adapter can communicate at up to a  
maximum rate of 230.4 kbps, place the jumper in the “divide by 2” position  
(marked DIV2).  
DIV1  
DIV2  
DIV4  
Figure 3-9. Clocking mode “divide by 2.”  
15  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
To enable the Adapter to reach its maximum possible data rate, 460.8 Kbps,  
place the jumper in the “divide by 1” position (marked DIV1).  
DIV1  
DIV2  
DIV4  
Figure 3-10. Clocking mode “divide by 1.”  
3.6 Baud Rates and Divisors for the “Div1” Mode  
The following table shows some common data rates and the rates you should  
choose to match them if you’re using the Adapter in the “Div1” mode.  
Table 3-2. Baud Rates for the “Div 1” Mode  
For this Data Rate  
1200 bps  
Choose this Data Rate  
300 bps  
2400 bps  
600 bps  
4800 bps  
1200 bps  
9600 bps  
2400 bps  
19.2 kbps  
57.6 kbps  
115.2 kbps  
230.4 kbps  
460.8 kbps  
4800 bps  
14.4 kbps  
28.8 kbps  
57.6 kbps  
115.2 kbps  
16  
 
CHAPTER 3: Card Setup  
If your communications package allows the use of baud-rate divisors, choose the  
appropriate divisor from the following table:  
Table 3-3. Divisors for the “Div 1” Mode  
For this Data Rate  
1200 bps  
Choose this Divisor  
384  
192  
96  
48  
24  
12  
8
2400 bps  
4800 bps  
9600 bps  
19.2 kbps  
38.4 kbps  
57.6 kbps  
115.2 kbps  
230.4 kbps  
460.8 kbps  
4
2
1
17  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
3.7 Baud Rates and Divisors for the “Div2” mode  
The following table shows some common data rates and the rates you should  
choose to match them if you’re using the adapter in the “Div2” mode.  
Table 3-4. Baud Rates for the “Div 2” Mode  
For this Data Rate  
1200 bps  
Choose this Baud Rate  
600 bps  
2400 bps  
1200 bps  
4800 bps  
2400 bps  
9600 bps  
4800 bps  
19.2 kbps  
38.4 kbps  
57.6 kbps  
115.2 kbps  
230.4 kbps  
9600 bps  
19.2 kbps  
28.8 kbps  
57.6 kbps  
115.2 kbps  
18  
 
CHAPTER 3: Card Setup  
Table 3-5. Divisors for the “Div 2” Mode  
For this Data Rate  
1200 bps  
Choose this Divisor  
192  
96  
48  
24  
12  
8
2400 bps  
4800 bps  
9600 bps  
19.2 kbps  
38.4 kbps  
57.6 kbps  
115.2 kbps  
230.4 kbps  
4
2
1
19  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
4. Installation  
IMPORTANT  
You MUST set up the operating system BEFORE you physically install  
the Card.  
4.1 Setting Up the Operating System  
If you are installing the PCI adapter in DOS, OS/2 , or QNX, please refer to  
the appropriate directory on one of the Serial Utilities Disks for instructions.  
®
4.1.1 WINDOWS 3.1X  
Refer to the Win3x.hlp file in the \Win31 directory on Disk 1 of the Serial Utilities  
software.  
4.1.2 WINDOWS 95/98 USERS  
If you are installing the PCI card in Windows 95/98, run setup on disk two of the  
Serial Utilities Diskettes before installing the card. Power down the computer and  
install the adapter. The resources are automatically configured for the PCI card.  
Refer to the appropriate help file in the Black Box folder located in the Start,  
Programs menu for changing those resources.  
Selecting the PCI COM Number in Windows 95  
When installing a PCI Serial Adapter in Windows 95 or 98, the default COM  
numbers assigned to the two ports will be COM5 and COM6 if those numbers are  
not already assigned. If they are assigned to other devices, the next available COM  
numbers will be assigned to the ports.  
To change the two ports so that Windows assigns them to COM3 and COM4:  
1. Double-click the “Systems” icon in the control panel or right-click on  
“My Computer” and choose “Properties,” which will bring you to  
“System Properties.”  
2. Choose the “Device Manager” tab and double-click on the “Multi-Function  
Adapter” heading. This will show all the information concerning the PCI  
Serial Adapter.  
3. Choose the “Resources” tab, which will show all resources assigned to the PCI  
Adapter. Uncheck the “Use Automatic Settings” box. Three input/output  
(I/O) ranges will be listed. The first I/O range is for the PCI bus and should  
not be changed. The second and third I/O ranges are the ones that need to  
be changed in order to have those ports set to COM3 and COM4.  
4. Double-click on the second I/O range, which will allow you to change the  
address. Highlight the entire I/O range and type 03e8–03ef for COM3. Click  
OK. Windows will inform you that you have made modifications that may  
affect other devices. Click OK.  
20  
 
CHAPTER 4: Installation  
5. Next, double-click on the third I/O range. Highlight the entire I/O range  
and type 02e8–02ef for COM4. Again, Windows will inform you that you have  
made modifications that may affect other devices. Click OK.  
Following these steps will change the COM: number assignments on the first  
two ports to COM3 and COM4.  
4.1.3 WINDOWS NT  
If you are installing a PCI card in Windows NT, run setup on disk two of the  
Serial Utilities Diskettes before installing the card. After the software installation  
is complete, power down the computer, install the card, then power up. Since  
resource allocation is automatic, the installation is now complete.  
4.1.4 DOS  
Refer to the Readme.txt file found in the \DOS directory on Disk 1 of the Serial  
Utilities software.  
4.1.5 OTHER OPERATING SYSTEMS  
Refer to the appropriate directory on Disk 1 of the Serial Utilities software.  
4.2 Installing the Hardware  
The Adapter has several jumper straps for each port that must be set for proper  
operation (see Chapter 3). Once you’ve done this, and have set up your operating  
system (see Section 4.1), take these steps to install the Adapter in any of your PC’s  
PCI expansion slots:  
1. Turn off PC power. Disconnect the power cord.  
2. Remove the PC case cover.  
3. Locate an available PCI slot and remove the blank metal slot cover.  
4. Gently insert the Adapter into the slot. Make sure that the adapter is seated  
properly.  
5. Replace the screw.  
6. Replace the cover.  
7. Connect the power cord.  
The Adapter should now be ready for continuous operation.  
21  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
5. Troubleshooting  
5.1 The Serial Utility Diskette  
The Adapter comes with a Serial Utility Diskette that has diagnostic software on it.  
We recommend that you always use this software first when you troubleshoot  
problems, because it can help resolve most common problems related to software  
and operating-system incompatibilities without requiring you to call Technical  
Support.  
1. Make sure the Adapter is securely installed in a motherboard slot.  
2. Use the supplied diskette and User Manual to verify that the Adapter is  
configured correctly. The supplied diskette contains the diagnostic programs  
“FindPCI,” “SSD” (for DOS), and “WINSSD” (for Windows NT, 3.1, or 95),  
which will verify if an adapter is configured properly. First, run the “FindPCI”  
utility and record the base I/O addresses and the IRQ assignments, these will  
be needed for SSD. Next, run the “SSD” diagnostic program (for DOS) or the  
“WINSSD” program (for Windows). Refer to the \dos\diag\diag.txt file on the  
supplied diskette for detailed instructions on using “SSD.”  
The Serial Utility Diskette might also contain README-style text files. You can  
consult these for information about issues that might have arisen since this manual  
was written, and for application-specific information.  
22  
 
CHAPTER 5: Troubleshooting  
5.2 Calling Black Box  
If you determine that the Adapter is malfunctioning, do not attempt to alter or repair  
it. It contains no user-serviceable parts. Contact Black Box Technical Support at  
724-746-5500.  
Before you do, make a record of the history of the problem. We will be able to  
provide more efficient and accurate assistance if you have a complete description,  
including:  
• current Adapter settings;  
• the nature and duration of the problem;  
• when the problem occurs;  
• the components involved in the problem (make and model of PC, other cards  
installed in it, the cables you’re using, etc.);  
• any particular application that, when used, appears to create the problem or  
make it worse;  
• the results of any testing you’ve already done.  
If possible, please also have the adapter installed in a computer ready to run  
diagnostics when you call.  
5.3 Shipping and Packaging  
If you need to transport or ship your Adapter:  
• Package it carefully. We recommend that you use the original container.  
• If you are returning the Adapter, make sure you include everything you  
received with it.  
Before you ship, contact Black Box to get a Return Authorization (RA) number.  
23  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
Appendix A: Interrupt Handling  
A.1 The Purpose and Early History of Interrupts  
A good analogy of a PC interrupt would be the phone ringing. The phone “bell” is  
a request for us to stop what we are currently doing and take up another task  
(speak to the person on the other end of the line). This is the same process the PC  
uses to alert the CPU that a task must be preformed. The CPU upon receiving an  
interrupt makes a record of what the processor was doing at the time and stores  
this information on the “stack”; this allows the processor to resume its predefined  
duties after the interrupt is handled, exactly where it left off. Every main sub-system  
in the PC has its own interrupt, frequently called an IRQ (short for Interrupt  
ReQuest).  
In these early days of PCs, the ability to share IRQs was an important feature for  
any add-in I/O card. Consider that in the IBM XT the available IRQs were IRQ0  
through IRQ7. Of these interrupts only IRQ2-5 and IRQ7 were actually available  
for use. This made the IRQ a very valuable system resource. To make the  
maximum use of these system resources, an IRQ-sharing circuit was devised that  
allowed more than one port to use a selected IRQ. This worked fine as a hardware  
solution but presented the software designer with a challenge to identify the source  
of the interrupt. The software designer frequently used a technique referred to as  
“round-robin polling.” This method required the interrupt service routine to “poll”  
or interrogate each UART as to its interrupt-pending status. This method of  
polling was sufficient for use with slower-speed communications, but as modems  
increased their throughput abilities this method of servicing shared IRQs became  
inefficient.  
24  
 
APPENDIX A: Interrupt Handling  
A.2 Why Use an Interrupt Status Port (ISP)?  
The answer to the polling inefficiency was the Interrupt Status Port (ISP). The ISP  
is a read-only 8-bit register that sets a corresponding bit when an interrupt is  
pending. Port 1’s interrupt line corresponds with bit D0 of the status port, Port 2’s  
with D1, etc. The use of this port means that the software designer now only has to  
poll a single port to determine if an interrupt is pending.  
The ISP is at “base+7” on each port. For example, if the base = 280 hex, the  
status port = 287 hex, 28F hex, and so on. The Adapter will allow any one of the  
available locations to be read to obtain the value in the status register. Both status  
ports on the Adapter are identical, so either one can be read.  
Example: This indicates that Channel 2 has an interrupt pending:  
Bit Position:  
Value Read:  
7
0
6
0
5
0
4
0
3
0
2
0
1
1
0
0
25  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
Appendix B: Connector Pinouts  
B.1 RS-232  
Table B-1. Pinout of Connector Set to RS-232  
Abbreviation  
TD  
Name  
Pin #  
Mode  
Transmit Data  
Request To Send  
Data Term Ready  
Ground  
3
7
4
5
2
1
6
8
9
Output  
Output  
Output  
RTS  
DTR  
GND  
RD  
Receive Data  
Data Carrier Detect  
Data Set Ready  
Clear To Send  
Ring Indicator  
Input  
Input  
Input  
Input  
Input  
DCD  
DSR  
CTS  
RI  
NOTE  
These pin assignments meet the EIA/TIA/ANSI-574 standard for RS-232  
DTE pinning on DB9 connectors.  
26  
 
APPENDIX B: Connector Pinouts  
B.2 RS-422/485  
Table A-2. Pinout of Connector Set to RS-422/485  
Abbreviation  
GND  
Name  
Pin #  
Mode  
Ground  
5
4
3
6
7
1
2
9
8
TX +  
Transmit Data Positive  
Transmit Data Negative  
Request To Send Positive  
Request To Send Negative  
Receive Data Positive  
Receive Data Negative  
Clear To Send Positive  
Clear To Send Negative  
Output  
Output  
Output  
Output  
Input  
TX-  
RTS+  
RTS-  
RX+  
RX-  
Input  
CTS+  
CTS-  
Input  
Input  
27  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
Appendix C: Electrical Interfaces  
C.1 RS-232  
Quite possibly the most widely used communication standard is RS-232. This  
implementation has been defined and revised several times and is often referred  
to as EIA/TIA-232.  
The IBM PC/AT computer defined the RS-232 port on a 9-pin D-subminiature  
connector, and subsequently the EIA/TIA approved this implementation as the  
EIA/TIA-574 standard. This standard is defined as the 9-Position Non-Synchronous  
Interface between Data Terminal Equipment and Data Circuit-Terminating  
Equipment Employing Serial Binary Data Interchange. Both implementations are  
in widespread use and are referred to as RS-232 in this document.  
RS-232 is capable of operating at data rates up to 20 kbps at distances less than  
50 ft. The absolute maximum data rate may vary due to line conditions and cable  
lengths. RS-232 is a single-ended or unbalanced interface, meaning that a single  
electrical signal is compared to a common signal (ground) to determine binary  
logic states. The RS-232 and the EIA/TIA-574 specification define two types of  
interface circuits: Data Terminal Equipment (DTE) and Data Circuit-Terminating  
Equipment (DCE). The Adapter is a DTE device.  
C.2 RS-422  
The RS-422 specification defines the electrical characteristics of balanced-voltage  
digital interface circuits. RS-422 is a differential interface that defines voltage levels  
and driver/receiver electrical specifications.  
On a differential interface, logic levels are defined by the difference in voltage  
between a pair of outputs or inputs. In contrast, a single-ended interface, for  
example RS-232, defines the logic levels as the difference in voltage between a  
single signal and a common ground connection.  
Differential interfaces are typically more immune to noise or voltage spikes that  
may occur on the communication lines. Differential interfaces also have greater  
drive capabilities that allow for longer cable lengths. RS-422 is rated up to  
10 megabits per second and can have cabling 4000 feet (1219.2 m) long. RS-422  
also defines driver and receiver electrical characteristics that will allow 1 driver and  
up to 32 receivers on the line at once. RS-422 signal levels range from 0 to +5 volts.  
RS-422 does not define a physical connector.  
28  
 
APPENDIX C: Asynchronous Communications  
C.3 RS-485  
RS-485 is backward-compatible with RS-422; however, it is optimized for partyline  
or multidrop applications. The output of the RS-422/485 driver is capable of being  
Active (enabled) or Tristate (disabled). This capability allows multiple ports to be  
connected in a multidrop bus and selectively polled.  
RS-485 allows cable lengths up to 4000 feet (1219.2 m) and data rates up to  
10 megabits per second. The signal levels for RS-485 are the same as those defined  
by RS-422.  
RS-485 has electrical characteristics that allow for 32 drivers and 32 receivers to  
be connected to one line. This interface is ideal for multidrop or network  
environments. RS-485’s tristate (not dual-state) driver will allow the electrical  
presence of the driver to be removed from the line. Only one driver may be active  
at a time, and the other driver(s) must be tristated.  
RS-485 can be cabled in two ways: two-wire and four-wire mode. Two-wire mode  
does not allow for full-duplex communication, so data be transferred in only one  
direction at a time. For half-duplex operation, the two transmit pins should be  
connected to the two receive pins (Tx+ to Rx+ and Tx to Rx). Four-wire mode  
allows full-duplex data transfers.  
RS-485 does not define a connector pinout, a physical connector, or a set of  
modem control signals.  
29  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
Appendix D:  
Asynchronous Communication  
In serial data communication, individual bits of a character are transmitted  
consecutively to a receiver that assembles the bits back into a character. Data rate,  
error checking, handshaking, and character framing (start/stop bits) are pre-  
defined and must correspond at both the transmitting and receiving ends.  
Asynchronous communications is the standard means of serial data  
communication for PC compatibles and PS/2 computers. The original PC  
was equipped with a communication or COM port that was designed around an  
8250 Universal Asynchronous Receiver Transmitter (UART). This device allows  
asynchronous serial data to be transferred through a simple and straightforward  
programming interface. A start bit, followed by a pre-defined number of data bits  
(5, 6, 7, or 8), defines character boundaries for asynchronous communications.  
The end of the character is defined by the transmission of a pre-defined number  
of stop bits (usually 1, 1.5, or 2).  
Odd  
Idle State  
of  
Line  
Even  
or  
Remain Idle  
or  
Next Start Bit  
Unused  
5 to 8 Data Bits  
1
Parity  
Bit  
0
1
1.5  
2
Stop Bits  
Figure D-1. Bit diagram for asynchronous communication.  
An extra bit used for error detection is often appended before the stop bits.  
This special bit is called the parity bit. Parity is a simple method of determining  
if a data bit has been lost or corrupted during transmission. There are several  
methods for implementing a parity check to guard against data corruption.  
Common methods are called (E)ven Parity or (O)dd Parity. Sometimes parity  
is not used to detect errors on the data stream. This is refereed to as (N)o parity.  
30  
 
APPENDIX D: Asynchronous Communication  
Because each bit in asynchronous communications is sent consecutively, it is easy  
to generalize asynchronous communications by stating that each character is  
wrapped (framed) by pre-defined bits to mark the beginning and end of the serial  
transmission of the character. The data rate and communication parameters for  
asynchronous communications have to be the same at both the transmitting and  
receiving ends. The communication parameters are baud rate, parity, number of  
data bits per character, and stop bits (usually listed in that order, like this:  
9600,N,8,1).  
31  
 
2-PORT RS-232/422/485 PCI HOST ADAPTER  
Appendix E: Board Layout  
• JxB JUMPER SETTINGS •  
RS422 - REMOVE ALL JUMPERS  
RS485 - AT= AUTO ENABLE  
RS485 - RT= RTS ENABLE  
RS485 - NE= NO ECHO  
Y1  
U6  
7201  
C1  
R1  
R2  
C10  
R29  
R30  
U1  
C2  
GD75232  
R8  
C12  
C13  
J1B  
J2B  
C4  
J1C J2C  
Port 2  
J1  
Port 1  
+
C5  
HEADER24PINW  
E1  
E2  
C14  
C11  
XC9536-7201  
Port 1  
R16 R20 R24  
R17 R21 R25  
R18 R22 R26  
HEADER24PINW  
E5  
E6  
C3 R4 R5 R8 R9 R10 R11  
R3 R5 R7  
J1A  
R12  
75174  
75175  
U4  
R13  
R14  
R15  
P
P
T
L
L
16550 PLCC  
PCI9050  
16550 PLCC  
R31  
U7  
U9  
J2  
Port 2  
GD75232  
C7  
U2  
J2A  
U4  
C15  
R27  
R28  
C8  
P
P
T
L
L
• JxC - CLOCK DIV •  
DIV1= DIVIDE BY 1  
DIV2= DIVIDE BY 2  
DIV4= DIVIDE BY 4  
R19 R23  
93CS46  
C6  
HEADER24PINW  
HEADER24PINW  
E3  
PORT1= J1x  
PORT2= J2x  
U5  
E4  
MADE IN USA  
• JxA JUMPER SETTINGS •  
P= PULL UP/DOWN ENABLE  
T= TERMINATION ENABLE  
L= CONNECT RX TO TX  
C16 C17  
C9  
U8  
P1  
Figure E-1. Board layout.  
32  
 
NOTES  
 
NOTES  
 
© Copyright 2000. Black Box Corporation. All rights reserved.  
1000 Park Drive • Lawrence, PA 15055-1018 • 724-746-5500 • Fax 724-746-0746  
 

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