YASPP (Yet another serial port problem)

John Kennedy johnk at opel.uu.net
Wed Dec 27 11:01:18 AEST 1989

In article <10740 at attctc.Dallas.TX.US> cassidy at attctc.Dallas.TX.US (Cassidy Lynar) writes:

> (serial device woes deleted)

Two problems come to mind:

1)  Is another device (typically the first parallel port) using int 5.
    This conflict would not manifest itself under dos, with its
    way of doing one thing at a time.

2)  Microport had a patchable bit mask that was used to write to the
    8259 interrupt controller.  If int 5 was not allocated as the OS was
    delivered, maybe something has to happen to enable it.

The fact that you're getting a character occasionally suggests to me
that a TxRDY interrupt is being looked for, but after a timeout
the next character is sent.  I can't image a serial driver that continues
to send under those conditions, but it may be some kind of a failsafe to
avoid an infinite wait in the driver.  My guess would be the first, a
conflict with another device.

Or, it could be a bug in the driver :-).


John Kennedy                     johnk at opel.uu.uunet
Second Source, Inc.
Annapolis, MD

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