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Old 03 September 2007, 19:04   #1
girv
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Reading the Real Time Clock

I'm looking for info on how to directly (= not using the OS) detect and read the RTC chips found in many big box Amigas and accelerator boards. There's a good archive on Aminet - ClockPeek.lha - that explains how to read the A2000 and A1200 clocks, but it leaves a couple of things out:
  1. How to detect which RTC is installed, if any.
  2. How to read the A3000 / A4000 clocks
  3. What are the possible clock types?
Does anyone have any other info? Thanks!
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Old 03 September 2007, 19:08   #2
Toni Wilen
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There are 2 different clock chips and they are semi-documented in WinUAE sources, cia.c but it may be quite difficult to understand
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Old 04 September 2007, 11:26   #3
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Not that difficult I've had a look at cia.c and also, FWIW, the Linux68k kernel sources, but there's still a couple of questions

Those two chip types cover all Amiga models ?

ClockPeek docs say that the clock chip registers are mapped to different addresses depending if you're on a 16-bit or 32-bit Amiga. Is that true? Does it depend on the processor being 16 (000/010) or 32 bit (020+), the chipram bus or something else?

How do you tell if a RTC is installed or not, and at which address ?

I guess I'll have to ReSource battclock ... erm ... resource
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Old 04 September 2007, 15:24   #4
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Attached is the datasheet for the MSM6242B RTC, used in 16 bit Amigas and normally mapped at 0xdc0000 to 0xdc003f. Some A2000 models map it somewhere else though, need to check my books.
Attached Files
File Type: pdf msm6242b.pdf (295.2 KB, 143 views)
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Old 04 September 2007, 17:33   #5
Toni Wilen
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Quote:
Originally Posted by girv View Post
Those two chip types cover all Amiga models ?
As far as i know (Haven't seen nothing else in schematics)

Both datasheets are easy to find.

Quote:
ClockPeek docs say that the clock chip registers are mapped to different addresses depending if you're on a 16-bit or 32-bit Amiga. Is that true? Does it depend on the processor being 16 (000/010) or 32 bit (020+), the chipram bus or something else?
???

A500, A1200 without expansions and A1200/68060 all show same results:

00DC0000 XX X0 XX X0 XX X1 XX X1 XX X2 XX X2 ...
...

X = garbage, "garbage type" depends on CPU, accelerator card etc..
Number = memory mapped clock register number

A2000 ("original" A2000 with DIP Agnus) has clock at 0x00d80000, other models have it at 0x00dc0000.


Quote:
I guess I'll have to ReSource battclock ... erm ... resource
Probably safest solution.
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Old 04 September 2007, 19:30   #6
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Cheers all, plenty to go on
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