TITLE
    DOS Compatibility Card: Serial Support vs. SoftWindows (8/94)
Article ID:
Created:
Modified: 		16131
8/29/94
8/29/94
TOPIC



    I have a MS-DOS program, that uses serial communications, that works fine on my Power Macintosh 6100 running SoftWindows, however it doesn't work on my Dos Compatible Quadra 610. The software vendor claims the problem is related to the way the Macintosh supports the RS-232. Is there a difference between the way the DOS Compatibility Card and SoftWindows handles serial support?

DISCUSSION


    Due to the RS-232 implementation of the Macintosh, not all RS-232 signals are
    available. These signals are not available: Carrier Detect (CD), Data Set
    Ready (DSR), Request to Send (RTS), and Ring Indicator (RI). If your
    application or serial device requires these signals, it will not work.

    The DOS Compatibility Card does not support Carrier Detect (CD). You must
    configure your communications applications so they do not use CD. Most
    communications applications can be set to respond to the CARRIER string sent
    back by most modems.

    The work around is for the customer to configure their software to use XON/XOFF
    for flow control. If their software does not allow for XON/XOFF then the
    software will not run on our DOS Card.

    The serial problem is the same for all Macintosh computers, but SoftWindows does some special software processing of serial signals to "emulate" the missing RS-232 signals. The SoftWindows manual has the following information:

    Serial Limitations-

    Programs that do not work well are those that are extremely timing sensitive, or that rely on serial port lines that are not available on the Macintosh serial port.

    SoftWindows has no access to the DSR, DCD or RI signals, and the RTS line cannot be set up, due to lack of lines. Instead, SoftWindows makes the DSR and RLSD/DCD lines seem to always have the same status as the DTR line. RI is always set to off.


    Support Information Services


Document Information
Product Area: Computers
Category: DOS Compatible
Sub Category: DOS Compatibility Cards
Keywords: hts,kwindows,kcompat,kppc

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