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DTINn may not be configured as a clock source when the timer
capture mode is selected or indeterminate operation will result.
• The 8-bit DTMRn[PS] prescaler value is set
• Using DTMRn[RST] the counter is cleared and started
• Timer events are either handled with an interrupt service routine, a DMA request or
by a software polling mechanism
21.3.1 Code Example
The following code provides an example of how to initialize DMA Timer0 and how to use
the timer for counting time-out periods.
DTMR0 EQU IPSBARx+0x400;Timer0 mode register
DTMR1 EQU IPSBARx+0x440 ;Timer1 mode register
DTRR0 EQU IPSBARx+0x404 ;Timer0 reference register
DTRR1 EQU IPSBARx+0x444 ;Timer1 reference register
DTCR0 EQU IPSBARx+0x408 ;Timer0 capture register
DTCR1 EQU IPSBARx+0x448 ;Timer1 capture register
DTCN0 EQU IPSBARx+0x40C ;Timer0 counter register
DTCN1 EQU IPSBARx+0x44C ;Timer1 counter register
DTER0 EQU IPSBARx+0x403 ;Timer0 event register
DTER1 EQU IPSBARx+0x443 ;Timer1 event register
* TMR0 is defined as: *
*[PS] = 0xFF,
divide clock by 256
*[CE] = 00
disable capture event output
*[OM] = 0
output=active-low pulse
*[ORRI] = 0,
disable ref. match output
*[FRR] = 1,
restart mode enabled
*[CLK] = 10,
system clock/16
*[RST] = 0,
timer0 disabled
move.w #0xFF0C,D0
move.w D0,TMR0
move.l #0x0000,D0;writing to the timer counter with any
move.l DO,TCN0 ;value resets it to zero
move.l #AFAF,DO ;set the timer0 reference to be
move.l #D0,TRR0 ;defined as 0xAFAF
The simple example below uses Timer0 to count time-out loops. A time-out occurs when
the reference value, 0xAFAF, is reached.
timer0_ex
clr.l DO
clr.l D1
clr.l D2
MOTOROLA
NOTE
Chapter 21. DMA Timers (DTIM0–DTIM3)
Using the DMA Timer Modules
21-9
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