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programing 8253 for pc

Posted on 1998-10-04
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Last Modified: 2012-06-21
i want to generate a accurate waveform in interrupt mode, timing about 1us, only i fear to handle timerchip. please give me programing solution.
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Question by:ksairampatro
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jack_p50 earned 50 total points
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Timer has 3 channels. Timer's interrupt is done by zero channel. Rate of timer interrupt
default is 18.2 Hz. This is calculated by 1.19 MHz/(zero channel counter). Default
counter=65536. To set rate to 50 Hz counter must be 1.19 MHz / 50 Hz = 23800=5CF8h
To program interrupt rate the controlling word must be in port 43h, and then you
need to write lower and then higher bytes in port 40h for 0 channel or in port 42h
for 2 channel.(1 channel is used to regenerate dynamic memory, so it cannot be used)
The controlling word format is :
Bits: 0            count type(0-binary,1-binary-decimal)
     1-3            mode 0-5 (0 and 2 channels use mode 3)
     4-5            operation(0-read current value,1-read/write lower byte,2-read/write higher
                     byte,3-read/write both bytes)
     6-7           channel number (0-2) or 3 - back reading
If you have questions, mail me (jack_p50@usa.net) or better contact through ICQ (number 17635851)
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