CHAPTER 6 16-BIT TIMER
6.4.3 Capture operation
The capture operation consists of latching the count value of 16-bit timer register 90 (TM90) into a capture
register in synchronization with a capture trigger, and retaining the count value.
Set TMC90 as shown in Figure 6-9 to allow the 16-bit timer to start the capture operation.
Figure 6-9. Settings of 16-Bit Timer Mode Control Register 90 for Capture Operation
TOD90 TOF90 CPT901 CPT900 TOC90 TCL901 TCL900 TOE90
TMC90
−
0/1
0/1
0/1
0/1
0
0/1
0/1
Count clock selection
Capture edge selection (see Table 6-3)
16-bit capture register 90 (TCP90) starts a capture operation after a CPT90 capture trigger edge is detected, and
latches and retains the count value of 16-bit timer register 90. The TCP90 fetches the count value within 2 clocks
and retains the count value until the next capture edge detection.
Table 6-3 and Figure 6-10 show the settings of the capture edge and the capture operation timing, respectively.
Table 6-3. Settings of Capture Edge
CPT901
CPT900
Capture Edge Selection
0
0
1
1
0
1
0
1
Capture operation prohibited
CPT90 pin rising edge
CPT90 pin falling edge
CPT90 pin both edges
Caution Because TCP90 is rewritten when a capture trigger edge is detected during TCP90 read, disable
the capture trigger edge detection during TCP90 read.
Figure 6-10. Capture Operation Timing (Both Edges of CPT90 Pin Are Specified)
Count clock
TM90
Count read buffer
TCP90
0000H 0001H
0000H 0001H
N
N
M
1
M
M
Undefined
N
M
Capture start
Capture start
CPT90
Capture edge detection
Capture edge detection
User’s Manual U15075EJ1V0UM00
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NEC [ NEC ]
