Configuring the PC serial ports

Your DOS-compatible Macintosh supports two serial ports, COM1 and COM2. You can assign these ports to an unused Macintosh printer port or modem port, to a text file for later processing, or to a setting of None.

mTo assign a Macintosh serial port to a COM port, make a selection in the COM port’s pop-up menu in the PC setup control panel.

When you assign a port to a text file, you specify a name and location for the file in a dialog box that appears. Macintosh serial ports already in use appear dimmed in the menu. (The printer port may be in use by AppleTalk, which may be used for a network or LaserWriter connection; the modem port may be in use by communications or fax software.) Changes to these selections take place immediately.

Assigned ports may not be available to the Mac OS: Mac OS programs may no longer be able to access ports that you’ve assigned to DOS. Allocate these ports only when they’re needed, and deallocate them when they’re no longer required by your DOS programs. (You won’t have to restart the computer to have the changes take effect.)

The maximum baud rate supported by the DOS-compatible Macintosh when a COM port is assigned to a Macintosh serial port is 19,200 bits per second (bps). However, when the MODE command is issued in DOS and the serial port is set at 19,200 baud, the incorrect message “Function not supported on this computer” is displayed. This occurs because DOS is looking for specific hardware (a PC UART) that is not emulated by the DOS-compatible Macintosh. The Macintosh actually does support 19,200 baud, and can be set by a number of communications application programs.

Configuring the PC Environment

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Apple 640 manual Configuring the PC serial ports