Capture Operation; Settings Of 16-Bit Timer Mode Control Register 20 For Capture Operation; Capture Operation Timing (With Both Edges Of Cpt20 Pin Specified); Settings Of Capture Edge - NEC PD789488 User Manual

6.4.3 Capture operation

The capture operation consists of latching the count value of 16-bit timer counter 20 (TM20) into a capture register
in synchronization with a capture trigger, and retaining the count value.
Set TMC20 as shown in Figure 6-8 to allow the 16-bit timer to start the capture operation.
Figure 6-8. Settings of 16-Bit Timer Mode Control Register 20 for Capture Operation
TOD20 TOF20 CPT201 CPT200 TOC20 TCL201 TCL200 TOE20
−
TMC20 0/1
16-bit capture register 20 (TCP20) starts a capture operation after a CPT20 capture trigger edge is detected, and
latches and retains the count value of 16-bit timer 20. TCP20 fetches the 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 settings of the capture edge and the capture operation timing, respectively.
CPT201 CPT200
0 0
0 1
1 0
1 1
Caution Because TCP20 is rewritten when a capture trigger edge is detected during TCP20 read, disable
capture trigger edge detection during TCP20 read.
Figure 6-9. Capture Operation Timing (with Both Edges of CPT20 Pin Specified)
Count clock
TM20 0000H
Count read buffer 0000H
TCP20
CPT20
Remark N, M = 0000H to FFFFH
116
CHAPTER 6 16-BIT TIMER 20
0/1 0/1 0/1 0/1
Table 6-3. Settings of Capture Edge
Capture operation prohibited
CPT20 pin rising edge
CPT20 pin falling edge
CPT20 pin both edges
0001H
0001H
Undefined
User's Manual U15331EJ4V1UD
0/1 0/1
Count clock selection
Capture edge selection (see Table 6-3)
Capture Edge Selection
N
N
N
Capture start
Capture edge detection
M 1 M
M
M
Capture start
Capture edge detection