We are using the MTIM module to generate an periodic interrupt for a software loop. When I fine tune the value in the MTIMOD register to get a 10Hz IRQ it works fine. I am toggling a bit to look at the period on a scope. Without changing and code if I reflash the part the value drops from 10.1Hz to 9.66Hz.
Could some one tell us what the problem could be?
; mov #%11000011,MTIMMOD ;load modulo counter value, do not change, 11000011 makes 10.0Hz MTIM IRQ's
; mov #%00010011,MTIMCLK ;select XCLK, prescale div 4, provides 100ms MTIM TOF IRQ's
; mov #%01100000,MTIMSC ;enable overflow interupts, reset and make counter active
; cli ; enable interrupts
; main loop
;Standby: wait ;wait for 100ms modulo timer interrupt to execute Main Loop
; bset 1,PTBD
; lda #1
; jsr DLYXMS
; bclr 1,PTBD
; bra Standby