Re: problems changing clock multiplier to 4X on the DS80C400

Koen Swinters wrote:
> Hello,
> 
> I'm trying to set the clock multiplier on 4x . For this I use the following
> code:
> ;
> ; Multiply crystal frequency by 4
> ;
> mov pmr, #10001000b ; Set for crystal * 4
> mov pmr, #10011000b ; Enable multiplier
> WaitCrystal:
> mov a, exif ; Wait for multiplier to be ready
> jnb acc.3, WaitCrystal ; Jump if CKRY is low
> mov pmr, #00011000b ; Go to crystal * 4
> 
> I've also written a small test program to test the speed of the
> DS80C400.this program just toggles a pin at full speed for a few msec with
> disabled interrupts.
> The axternal cristal frequency is 14.7456MHz.
> Can someone tell my what is going wrong with changing the clock multiplier
> to 4X and how i can solve this.

Koen,

I am assuming that you have a custom board (not a TINIm400) with fast 
flash or RAM for execution.

1. Verify the timings of your specific RAM/Flash at ~60MHz
2. Try a slower crystal, like 11.0592MHz to give the critical timings 
some extra margin


-- 
--
Bryan Armstrong
bryan.armstrong-6tN4nzCoH/[email protected]

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