Hi André,
Andre Fachat wrote on November 19, 2001 11:36 PM:
> As far as I understand the PC LPT port is simply too slow to handle the
> maximum data transfer rate. So I doubt that full synchronized access is
No, it's not necessarily too slow.
You're right, most parallel ports are part of the I/O address space and
indeed, are too slow. Anyway, there are parallel ports out there which
are part of the memory address space, and they should be fast enough!
For example:
With the "normal" I/O address space setup, I once used a PC (Pentium-150)
as a "digital oscilloscope" with a resolution of 4us (with a hand-written
and optimized sampling loop in assembler). Changing to memory mapped con-
figurations, one shoud easily be able to get at least an eighth of this
time.
> Is there a good enough timer available in the PC?
You have the time stamp counter (TSC) on Pentium and above (and on some
486, too). It's resolution is the processors frequency, and it can be
used very good as a time base, so I think it should be accurate enough.
Look up the RDTSC command.
Spiro.
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