Changes to COMMDRV.IBM for Advanced Revelation 2.1

To take advantage of capabilities offered by 80286, 80386, and 80486-based computers, several changes have been made to COMMDRV.IBM, the communications device driver provided with Advanced Revelation.

In previous versions, COMMDRV.IBM supported COM1 or COM2 on the standard DOS communications IRQs and at the standard port addresses. This has been enhanced to allow the user to specify both the IRQ level and the port address to use. In addition, an optional installation message is available. The new options are specified on the command line in the computer's CONFIG.SYS file as were the old options. Full backward compatibility has been maintained, so any existing applications do not require changes.

The old syntax is:

DEVICE=COMMDRV.IBM {buffer_size} {,com_number}

The new syntax is:

DEVICE=COMMDRV.IBM {/V} {buff_size} {,com_numb} {,port_address} {IRQ_level}

The first parameter, "/V" or "/v", will, if added to the front of the command line, display a "verbose" installation message. The default is not to display the message. The message displays the values for all specifiable parameters or a failure message.

The next two arguments are as before except that the COM number may be any integer from 1 to 4, inclusive.

The third argument, port_address, is used to specify a non-standard port address to which to install. This argument is specified in decimal but is displayed in hex on the install message. This lets you verify that the value is correct.

The default values are based on the com number:

The last argument, any number between 2 and 15, specifies the IRQ level. It is up to you to specify an IRQ level that will work on your machine. This value defaults to IRQ 4 for COM1 and COM3, and IRQ 3 for COM2 and COM4.

If a COM number is specified, you can provide the port address, the IRQ level, or both.

To install the COM driver on more than one port at a time, a copy of the driver must be made for each port and the internal device name must be changed in each COM driver file.

First, make a copy of the driver:

COPY DOS COMMDRV.IBM TO:(DOS COMMDRV2.IBM

Using the Advanced Revelation editor, edit the driver object code:

EDIT DOS COMMDRV2.IBM

Locate the characters "COMM$ " in the object code and change any of the characters in the name without changing the name's total length. The name must be eight characters long.

For example, you can change the name to "COMx$ " where "x" is the number of the com port being used.

Warning: Changing the length of the object code will make it unusable.

Save your changes by pressing [F9] and exit. Repeat the process for each driver needed.

If the device name is not the default "COMM$ ", the -DEVICE switch must be used when entering TERMINAL. This tells the terminal program to look for another copy of the driver instead of the copy with the standard name.

The fact that DOS supports only COM1 through COM4 does not limit the COM driver to 4 installations. The limitations are the amount of memory that the buffer for COM port data will use on the computer and the number of available interrupt lines on the computer.