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RE: Exercising a serial port

At 04:47 PM 10/20/2003 +0000, Alan P. Biddle wrote:

>Another useful discussion!!  However, I will need to do some looking as I
>MUST access a PCI card, COM3&4, which so far as I know does not have DOS
>drivers.  Someone else suggested a PIC programmer,  which has a test mode to
>"wiggle the lines."  Looks promising, but have not had time to verify it
>does what I want.

Hi Alan,

The trick I suggested using "debug" will work on PCI cards. You
do not need a DOS driver. Here is how it works:

Windows does not really let you touch the hardware. When the
debug program does an I/o access, the PC hardware
generates a trap which is fielded by the Windows, DOS emulator.
Windows then figures out what you had intended and (if safe)
does the equivalent for you under Windows.

However, some PCI serial cards are not hardware compatible so
this may or may not work depending on your card. I would try it - j
ust add 4 hex to the base address of your COM3 or COM 4. Best of luck!

Tony AA2TX

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