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Memory Map/Register Definition
MCF5271 Reference Manual, Rev. 2
Freescale Semiconductor
22-7
22.2.9 DMA Timer Reference Registers (DTRRn)
Each DTRRn, shown in
Figure 22-5, contains the reference value compared with the respective
free-running timer counter (DTCNn) as part of the output-compare function. The reference value
is not matched until DTCNn equals DTRRn, and the prescaler indicates that DTCNn should be
incremented again. Thus, the reference register is matched after DTRRn+1 time intervals.
Table 22-4. DTERn Field Descriptions
Bits
Name
Description
7–2
—
Reserved, should be cleared.
1
REF
Output reference event. The counter value, DTCNn, equals the reference value, DTRRn.
Writing a one to REF clears the event condition. Writing a zero has no effect.
0
CAP
Capture event. The counter value has been latched into DTCRn. Writing a one to CAP
clears the event condition. Writing a zero has no effect.
REF
DTMRn[ORRI]
DTXMRn[DMAEN]
0
X
No event
1
0
No request asserted
1
0
1
No request asserted
1
0
Interrupt request asserted
1
DMA request asserted
CAP
DTMRn[CE]
DTXMRn
[DMAEN]
0
X
No event
1
00
0
Disable capture event output
1
00
1
Disable capture event output
1
01
0
Capture on rising edge & trigger interrupt
1
01
1
Capture on rising edge & trigger DMA
1
10
0
Capture on falling edge & trigger interrupt
1
10
1
Capture on falling edge & trigger DMA
1
11
0
Capture on any edge & trigger interrupt
1
11
1
Capture on any edge & trigger DMA