HAHN_K@DMRHRZ11.BITNET (06/24/87)
I'm still trying to install my own timer, and stumbled over the
'fact', that the system's timer ('C') is said to generate a 200hz-
interrupt... As far as I can see it's installing procedure uses a
division factor of 64 (decimal, I suppose), and a counter that's
set to 192 (C0 hex). IF I believe my documentation which says that
the MFP 68901 uses a 4Mhz - clock cycle, then what? All the divisions
mentioned above wouldn't at all generate a 200hz-interrupt. Am I
wrong? What I need are the data and control values for getting a
one-millisecond resolution.
Any suggestions?
Yours in advance, Klaus.
-- Klaus Hahn --
<HAHN_K@DMRHRZ11.bitnet>fischer-michael@YALE.ARPA (Michael Fischer) (06/24/87)
I'm still trying to install my own timer, and stumbled over the
'fact', that the system's timer ('C') is said to generate a 200hz-
interrupt... As far as I can see it's installing procedure uses a
division factor of 64 (decimal, I suppose), and a counter that's
set to 192 (C0 hex). IF I believe my documentation which says that
the MFP 68901 uses a 4Mhz - clock cycle, then what? All the divisions
mentioned above wouldn't at all generate a 200hz-interrupt. Am I
wrong? What I need are the data and control values for getting a
one-millisecond resolution.
Any suggestions?
Yours in advance, Klaus.
A 200hz interrupt has a 5 millisecond period. The numbers you give
are not far off, if the '64' is interpreted as a hex number (= 100 decimal),
for then the timer would interrupt every 100*192 clock cycles, or every
19.2/4 = 4.8 milliseconds.
--Mike Fischer
Arpanet: <fischer@yale.arpa>
Bitnet: <fischer@yalecs>
-------jwt@atari.UUCP (Jim Tittsler) (06/26/87)
In article <8706240140.AA17054@ucbvax.Berkeley.EDU>, HAHN_K@DMRHRZ11.BITNET writes: > ... As far as I can see it's installing procedure uses a > division factor of 64 (decimal, I suppose), and a counter that's > set to 192 (C0 hex). IF I believe my documentation which says that > the MFP 68901 uses a 4Mhz - clock cycle, then what? The MFP in the ST series is clocked at 2.4576 MHz (a number that generates "correct" baud rates). Therefore 2.4576 MHz prescaled by the divide by 64 (decimal) and then divided by 192 (decimal) produces a 200 Hz clock. Jim Tittsler, sort of a hardware guy, Atari Corp. {ames, sun}!atari!jwt