Following my previous e-mail with respect to detecting a 60-200 kHz TTL signal wich generates an interrupt throug an ISA based PIO-24 card:
The response-time of one interrupt is 6-7 mirosecond meaning a frequency of 150 kHz. However detecting a frequency above 25 kHz goes with a deviation. Probably caused bij the the timer interrupts. Studying the code and doing a few timing experiments leads me to these conclusion: A real-time Timerinterrupt is invoked every 5 millisecond and lasts 9-13 microseconds. A part of the RT-timer ISR can be interrupted by other real-time interrupts. The Linux Timer interrupt is invoked every 10 ms (this is a mean, it fluctaties between 6 and 400 ms) and lasts 30 -70 micoseconds. Does anyone know whether linux interrupts (i.e. keyboard, hard-disk-IDE0, PS2/mouse, ehternet and above all the timer interrupts) always can be interrupted by real-time interrupts? Normally the linux timer ISR is started with the SA-INTERRUPT flag which means NO interrupts. - Has anyone experience with enabling interrupts in a real-time ISR (normally all interrupts are disabled). I fear deadlocks with the real-time Timer-interrupts or very long interrupt response times. Greetings, Erwin Triepels -- [rtl] --- To unsubscribe: echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR echo "unsubscribe rtl <Your_email>" | mail [EMAIL PROTECTED] -- For more information on Real-Time Linux see: http://www.rtlinux.org/
