HIGH SPEED DUAL ASYNCHRONOUS SERIAL BOARD

INTRODUCTION

ABOUT YOUR SERIAL BOARD

Congratulations on your purchase of the dual serial board! It combines the
convenience of two serial port connectors, each incorporating a 16550AN UART,
with throughput capability of up to 115.2K bits per second (bps). Your serial
board is a 100% IBM PC-compatible, internal half card, equipped with two DB-9
(9-pin) serial port connectors labeled Channels A and B. It can be used for 
modems, printers, mouse devices and other serial equipment.

CABLE REQUIREMENTS

You'll need two RS-232 cables to connect two serial devices to the serial 
board. Use shielded cables to ensure minimal interference with radio and 
television reception.

The ports on your serial board each require a DB-9 female (socket) connector 
at one end of each cable. Check your peripheral devices to determine what
types of connectors they require at the other end. Two common RS-232 
connectors are DB-9 and DB-25 female or male (plug). Your local distributor 
should be able to supply you with the proper cable. We recommend that your 
cable length not exceed 6 feet.


PRE-INSTALLATION

SELECTING COM PORTS

Each port on your serial board requires a serial port address: COM1, COM2, 
COM3, or COM4. The board's factory settings are COM1 for the Channel A port 
and COM2 for the Channel B port.

If you already have a serial device at COM1 and/or COM2 on your computer, you 
will need to use the address(es) COM3 and/or COM4 for the new serial ports. To
assign the new COM port address(es), you'll need to change the COM port jumper
switches that are illustrated in Figure 1, J1 through J4.

Each COM port jumper has three upright contacts, and a shunt over two of the
contacts sets the switch for that COM port. In Figure 1, the dark areas in the
expanded view of J1 and J2 indicate which contacts are covered when the board
is shipped. For Channel A, the shunt is over the left and center contacts of
the COM1 switch. For Channel B, the shunt is over the right and center
contacts of the COM2 switch.

If you have to change a factory-set COM port because you already have one or
two serial devices installed, you may also have to change the corresponding
Interrupt Request (IRQ). Software such as communications programs and printer
drivers use IRQs to instruct the computer to stop the processor's current 
operation in order to perform other operations.

WARNING: In order to set up your serial operations without conflicting IRQs, 
review the following information before you change a COM port or IRQ. You may
also need to review your application software manual to find out which COM 
ports and IRQs your software supports.

There are five possible IRQs for each port/channel on the serial board: IRQs 2
through 5 and IRQ7, labeled I2, I3, and so on. Each IRQ jumper switch has two
contacts, with a shunt covering (and thereby enabling) the selected IRQ.

SELECTING AN INTERRUPT REQUEST (IRQ)

IBM-compatible computers reserve IRQ4 for COM1 and IRQ3 for COM2, as shown in
the table below. All IBM PC-compatible programs and device drivers support 
these reserved IRQs for those two serial ports.

          Serial          Serial Port
          Port    IRQ     Address (Hex)
          ----    ----    -------
          COM1    IRQ4    3F8-3FF
          COM2    IRQ3    2F8-2FF
          COM3    IRQ4    3E8-3EF
          COM4    IRQ3    2E8-2EF

If you need to use COM3 or COM4, you may be able to use IRQ4 or IRQ3, as shown
in the table. However, keep the following information in mind.

1. To select COM3 or COM4, lift the shunt off the switch of the COM port you 
   want to change, and replace it over the two corresponding contacts of your 
   selected COM port.

   NOTE: Be sure that the Channel A jumper shunt covers the left and center 
   contacts, and that the Channel B jumper shunt covers the right and center 
   contacts. When you are finished, one jumper should be to the left, the 
   other to the right.

2. To enable a different IRQ, lift the Channel A or Channel B shunt off the
   IRQ you are changing, and replace it over the two contacts of your selected
   IRQ for that channel. Do not enable two IRQs for the same channel.

3. To disable an IRQ because it isn't needed, lift the shunt off the switch of
   the enabled IRQ. Replace the shunt so that it straddles one pin each of two
   adjacent IRQs. for example, I4 and I5. This does not make any connection,
   but keeps the shunt handy in case you wish to enable an IRQ for that serial
   port again.

TROUBLESHOOTING

If a device that you have attached to the serial board is not working 
properly, try the following:

1. Attach the device to a serial port other than one on the dual serial board 
   to make sure that the problem is not with the device.

2. If your device was previously attached to a different serial port, you may 
   have to change your device's software setup to reflect its new COM port
   address and IRQ.

3. If problems occur while using high throughput speeds, make sure the RS-232 
   cable does not exceed 6 feet.

4. If you still encounter problems, review the previous information on 
   selecting COM ports and IRQs. You may find conflicting COM port addresses
   or IRQs. Review the software parameters you have set, also, to be sure you
   specified the correct COM ports.

DB-9 PIN ASSIGNMENTS

The following chart shows the pin assignments and signal source for a DB-9 
connection to your serial board.

Function             DB-9    Signal Source
-------------------  ----    --------------
Transmitted Data      3      Computer
Received Data         2      Serial Device
Request to Send       7      Computer
Clear to Send         8      Serial Device
Data Set Ready        6      Serial Device
Signal Ground         5      Both Directions
Carrier Detect        1      Serial Device
Data Terminal Ready   4      Computer
Ring Indicator        9      Serial Device
