Help with AP8 (OSC-CRISTAL)

[alecelario]

Hello, i have an AP8 and this work perfect with the internal oscilator, but a need use the cristal oscilator. I make a routine to configurate pctl,pmsh,pmsl,pmrs,pmds and pbwc register but doesn´t work. The routine is:

  mov     #%00111001,config1     
  mov     #%00000001,config2     
  mov     #%00000001,pctl               ;programo P=$0, E=$0   
  mov     #%00000001,pmsh            ;programo N=$F5 con pmsh y pmsl

   mov     #%11101001,pmsl             ;programo N=$F5 con pmsh y pmsl
  mov     #%01000000,pmrs             ;programo L=$40
  mov     #%00000001,pmds            ;R=$1
   bset    5,pctl                                ;enciendo el PLL con el bit PLLON=1
  bset    7,pbwc          ;pongo en modo automático en PLL con el bit AUTO=1  
waitPLL:
   brclr 6,pbwc,waitPLL  ;salta a waitPLL si el bit LOCK=0

                                  ;( frecuencia  incorrecta o variable)

   bset  4,pctl                ;sino sigue y engancha a frecuencia del PLL

           
 Los parámtros P,N,L,E son para Fbus=2MHz,    GCMVCLK=GCMPCLK=8MHz

What is the problem?

[rocco]

Hi, Alecelario:

Just a guess:

Is this the first time you have written to Config1 or Config2? Could other initialization code have written to the previously?

Config1 and Config2 are "Write-once" registers. If they have been previously written since reset, any further writes will be ignored.

[peg]

Hi Alecelario,

Firstly, this is a non-A AP8?

What frequency is your crystal?

You have not shown the value in the MOR register.

The value in CONFIG2 for bits 3:4 you show as 0:0, this is for internal oscillator.

1:0 is crystal.

Regards

Peg