CHAPTER 6 16-BIT TIMER
User's Manual U11919EJ3V0UM00
102
6.4.3 Capture operation
The capture operation functions to capture and latch the count value of 16-bit timer counter 20 (TM20)
synchronizing with a capture trigger.
Set as shown in Figure 6-8 to allow the 16-bit timer to start the capture operation.
Figure 6-8. Setting Contents of 16-Bit Timer Mode Control Register 20 during Capture Operation
-
0/1
0/1
0/1
0/1
0
0/1
0/1
TOD20 TOF20 CPT201 CPT200 TOC20 TCL201 TCL200 TOE20
TMC20
Count Clock Selection
Capture Edge Selection (see Table 6-3)
16-bit capture register 20 (TCP20) starts capture operation after being detected a CPT20 capture trigger edge,
and latches and retains the count value of 16-bit timer counter 20. TCP20 fetches count value within 2 clocks and
retains the count value until the next capture edge detection.
Table 6-3 and Figure 6-9 show the setting contents of capture edge and capture operation timing, respectively.
Table 6-3. Setting Contents of Capture Edge
CPT201
CPT200
Capture Edge Selection
0
0
Capture operation prohibited
0
1
CPT2 pin rising edge
1
0
CPT2 pin falling edge
1
1
CPT2 pin both edges
Caution
Because TCP20 is rewritten when a capture trigger edge is detected during TCP20 read, disable
the capture trigger detection during TCP20 read.
Figure 6-9. Capture Operation Timing (Both Edges of CPT2 Pin are Specified)
Count Clock
TM20
Count Read Buffer
TCP20
CPT2
0000H
0000H
0001H
0001H
Undefined
N
N
N
M
-
1
M
M
M
Capture Start
Capture Start
Capture Edge Detection
Capture Edge Detection
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