Bart Vandewoestyne wrote:
> i have to be able to measure with an accuracy of 0.001 micro sec.
You mean 1 nanosecond?
Independent from the operating system, this is not managable
with the parallel-port of a PC, since each read access will take
about one microsecond: the read has to go the way from the
CPU via Host-Bridge via PCI/ISA-Bridge to the SuperI/O-Chip.
No chance at all to measure 1 nanosecond directly in a loop!
Even when using the interrupt line of the parallel-port,
the latencies caused by the intel-(mainboard)-architecture
are much higher than a microsecond.
You might connect an external counter, but up to 1 GHz,
thatīs realy not cheap!
<YOKE>
Another solution might be very funny: AFAIK, the time stamp
counter is clocked with the speed of the CPU, for example
500MHz (2ns). You could directly use one of the unused
LINT-lines of the processor, but you will still have some
latencies (about 10ns, AFAIR). Also, it wonīt be a simple
task to design the necessary circuit ...
</YOKE>
What exactly is the application, maybe there are other
solutions ...
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