I'm trying to port old HC11 code (written by another employee) to the MC9S12A32, and this is my first attempt at working with the Motorola/Freescale family of MCUs.
The problem I'm seeing is that the C0F flag is immediately set when I initialize the timer (by enabling the Output Compare on Channel 0 and enabling the timer by setting TEN) :
TIMERINIT LDAA #$01
STAA TIOS ;SET CHANNEL 0 TO OUTPUT COMPARE
STAA TSCR1 ;ENABLE TIMER
Later, when I'm trying to create a 15ms delay, the C0F flag is already set and my delay subroutine exits too quickly. I have tried to clear the C0F flag by writing a 1 to the bit (TFLG1.1), but that either fails or the flag is immediately set again before I can read it with the next instruction
STAA TFLG1 ;CLEAR OC0F
LDD TCNT.H ;GET PRESENT TIMER VALUE
ADDD DLY ;ADD REQUIRED DELAY
STD TC0.H ;STORE IN COMPARE 0
LP1 LDAB TFLG1 ;WAIT FOR COMPARE
BRCLR TFLAG, $01, LP1
Can anyone offer a suggestion why the C0F flag is being set immediately and/or continuously?
Also, as a side question, in CodeWarrior, there doesn't seem to be an easy way to watch the Timer registers change as I step through instructions (which would make this problem easier to diagnose). My Memory window doesn't update the contents of memory locations as I step through--should this be the case?
Thanks in advance.