Appendix B - Configuring Serial/Parallel Adapters
This appendix provides information about serial/parallel adapters. "Adding a Serial/Parallel Adapter to Your Banyan Server" details how to configure a serial/parallel adapter in the Banyan server software. The rest of this appendix details how to configure the IBM Serial/Parallel adapter, a card that provides one serial port for ISA-bus servers. (For MCA-bus servers, use the dual asynchronous adapter. For details on installation, refer to the documentation that comes with the card.)
If your ISA-bus server contains an IBM Serial/Parallel adapter, use the information in this appendix to determine a workable configuration for your server. If your ISA-bus server contains a non-IBM Serial/Parallel adapter, refer to the manufacturer's documentation for information about disabling interrupts.
Note: Interrupts are a scarce resource. Banyan server software does not require interrupts for serial and parallel ports, but the IBM adapter is shipped with a configuration that uses interrupts. You may need to disable interrupts on the card to free them for use by a LAN or serial communications card.
Adding a Serial/Parallel Adapter to Your Banyan Server
You must add a Serial/Parallel adapter as both a parallel port and a serial port using the Add/Change Card screen. To disable the slot and interrupt value, enter 0 for the interrupt.
If you specify slot 0 and interrupt 0 keep in mind that you still have a limited amount of resources for the card. For example, a parallel port has only three I/O addresses available for use. Consequently, you may specify slot 0 and IRQ 0 for each card, but you are still limited to three cards. Similarly, if you specify slot 0 and interrupt 0 for a Serial Port card, you are limited to configuring two of these cards since there are only two I/O addresses available.
Configuring the IBM Serial/Parallel Adapter for an ISA-bus Server
The configuration of a Serial/Parallel adapter is controlled by modules that connect sockets in two locations. Each module has two vertical columns of pins, with four pins on each side. Two pins in one column are connected by traces to two pins in another column. Either the upper-two or lower-two pins in each column are connected in this fashion.
The modules plug into the two locations marked J1 and J2 on the lower-left part of the card, as shown in Figure B-1. Location J1 configures the serial port on the card. Location J2 configures the parallel port.
Each location has eight sockets to accommodate the pins on the module. Each socket forms a pair with the socket directly across from it. A socket pair is connected when the corresponding pins on the module are connected by a trace. For ease of description, socket pairs at each location are identified by using the numbers 1 through 4, from top to bottom, as shown in Figure B-2.
The positioning of the module determines which interrupts and I/O Addresses are used for the serial and parallel ports that the adapter provides. For example, Figure B-2 shows a module with two traces cut, disconnecting socket pairs 3 and 4.
Each module can be in one of two positions. When a module is positioned so that sockets 3 and 4 are connected, it is in position A. When a module is positioned so that sockets 1 and 2 are connected, it is in position B. Figure B-3 shows the two positions.
The adapter is usually shipped with both modules at location J1 and J2 in position A.
At each location, socket pairs 1 and 3 control interrupts. Since Banyan server software does not use interrupts for parallel or serial ports, positions A and B both use resources that the server software does not require.
You can disable the interrupt normally used by a port so another device can use it. To do so, you must cut a trace on a module. For example, if you cut the trace at socket pair 3 of a module in position A, there is no connection for the interrupt. The interrupt is then available for use by other cards in the server, as shown in Figure B-4.
If you cut a trace, you cannot use the module in another position. For example, if you cut a trace on a module in position A, the module will not work in position B. If you need to replace a module later, they are inexpensive and available commercially. Table B-1 lists the resources used by the Serial/Parallel adapter. The first five columns explain what resource values and devices are affected by the modules in different positions and locations on the card. To disable interrupts, cut the traces at the socket pair identified in the last column.
Location | Position | Interrupt | I/O Address | Port Name | Device | To Disable, Cut Trace At |
J1 | A | 4 | 3F8 | Serial Port 1 | COM 1 | 3 |
J1 | B | 3 | 2F8 | Serial Port 2 | COM 2 | 1 |
J2 | A | 7 | 378 | Parallel Port 1 | LPT 1 | 3 |
J2 | B | 5 | 278 | Parallel Port 2 | LPT 2 | 1 |