HCS12 Assembly controlling frequency with PPL

Thread Starter

justtrying

Joined Mar 9, 2011
330
I am trying to write a code to double frequency of bus clock. Here is what I have:

Rich (BB code):
PROGRAM_ADD     EQU     $0800

PLLCTL  EQU     $003A
CLKSEL  EQU     $0039
SYNR    EQU     $0034
REFDV   EQU     $0035
FREQUENCY_ADD   EQU  $0900

        ORG  FREQUENCY_ADD

SYN_MULT        DB      $0
REF_DV          DB      $1

        ORG     PROGRAM_ADD

        BSET    PLLCTL,$01000000        ;turn PLL on 
        MOVB    SYN_MULT,SYNR
        MOVB    REF_DV,REFDV
        
        SWI
I am really unsure about it. All I know is that the steps are to turn PLL on and provide appropriate status to SYNR and REFDV. I think I did that, but I feel like it is wrong...
 
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