MPC5200 baud rate frequency

I have a Freescale MPC5200 board I designed a while ago which comes out of reset (I am writing the flash with a debug monitor which has served me over the years - I wrote it first for the 68020, then I made a CPU32 version, then an MPC8240 version etc...), and the monitor says something through the UART (I use PSC_6).

But the baud rate is totally off the mark.

I made the other system say the same through its UART and, measuring the length (43 characters, enough to get an idea if speeds match) I see the new system is apr. 2.7 times slower than it should be.

Great, I though I'd just write a 2.7 times lower value in the counter timer and see what happens. Well, the thing is, nothing happened. Same time (2.7 times what it should be) again. I just love that kind of thing when you make dramatic changes only to achieve no change. I am writing to the so called Counter Timer Upper and then Lower registers, treat them as 8 bit wide (i.e. I write using a .b access, stb) and I write the value of 215, which should yield a 19200 baud given the 132 MHz IPB clock. I already described the effect of changing the 215 to 79 (or sort of, I lost the precise number, it was not exactly 2.7, so it may have been 78 or 80, not that it matters).

I am tired now and will reluctantly go to sleep (I hate doing that with unsolved basic issues like that). Hopefully someone will have an idea what am I doing wrong which will help me tomorrow...



------------------------------------------------------ Dimiter Popoff Transgalactic Instruments

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Not being familar with that hardware I see three possible mistakes.

I hope the new day has brought you success.

1> you were writing the correct value but later overwriting it 2> you were writing the correct value but to the wrong location 3> you were writing the correct value but with an incorrect setup

It may be worth checking the errata in the hardware documentation. Bye. Jasen

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Ah, it did, thanks. There had been more to it than just the baud rate, I rewrote the UART initialization code in a less ambitious manner (thus more reasonable for a first-time out of reset CPU type here) and it worked.


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