How to produce a fast clock output?

[Amundsen Zhuang]

I want to produce a clock output on the pin of parallel port. I used
SIGALRM to implement it, and I only got a clock output with
20ms-cycle.

How could I produce a clock output that's cycle is 20us?

[phil-news-nospam@ipal.net]

On 5 Aug 2003 01:22:48 -0700 Amundsen Zhuang <a_roald@hotmail.com> wrote:
| I want to produce a clock output on the pin of parallel port. I used
| SIGALRM to implement it, and I only got a clock output with
| 20ms-cycle.
|
| How could I produce a clock output that's cycle is 20us?

I presume you want 10us on, 10us off. How accurate does it need to be?

1. Hack the parallel port driver to spin in a loop toggling the port at the
right time. Good luck.

2. Use the sound card instead of the parallel port, and output a wave file
consisting of on and off. Be sure it can do 100 K samples / second.

--
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| Phil Howard KA9WGN | [url]http://linuxhomepage.com/[/url] [url]http://ham.org/[/url] |
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[Fletcher Glenn]

Amundsen Zhuang wrote:

>
> I want to produce a clock output on the pin of parallel port. I used
> SIGALRM to implement it, and I only got a clock output with
> 20ms-cycle.
>
> How could I produce a clock output that's cycle is 20us?

You can't, unless you can gain exclusive use of the CPU. If you
did this, the system would no longer work. All UNIX tasks are
subject to time-slicing, meaning that you can only use so much
time before the system cuts over to another task. During the time
that the system is processing these other tasks, your task is
suspended.

--
Fletcher Glenn
email [email]f-g-l-e-n-n@quest.com[/email] (remove the dashes)