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CHAPTER 8 16-BIT TIMER/EVENT COUNTER
User’s Manual U12697EJ3V0UM
8.4.3 Pulse width measurement
16-bit timer counter 0 (TM0) can be used to measure the pulse widths of the signals input to the TI00/P35 and
TI01/P36 pins.
Measurement can be carried out with TM0 used as a free-running counter or by restarting the timer in
synchronization with the edge of the signal input to the TI00/P35 pin.
(1) Pulse width measurement with free-running counter and one capture register
If the edge specified by the prescaler mode register 0 (PRM0) is input to the TI00/P35 pin when 16-bit timer counter
0 (TM0) is used as a free-running counter (refer to
Figure 8-10
), the value of TM0 is loaded to 16-bit capture/
compare register 01 (CR01), and an external interrupt request signal (INTTM01) is set.
The edge is specified by using bits 4 and 5 (ES00 and ES01) of prescaler mode register 0 (PRM0). The rising
edge, falling edge, or both the rising and falling edges can be selected.
The valid edge is detected through sampling at a count clock cycle selected by prescaler mode register 0 (PRM0),
and the capture operation is not performed until the valid level is detected two times. Therefore, noise with a
short pulse width can be rejected.
Figure 8-10. Control Register Settings for Pulse Width Measurement with
Free-Running Counter and One Capture Register
(a) 16-bit timer mode control register 0 (TMC0)
0
0
0
0
TMC03
0
TMC02
1
TMC01
0/1
OVF0
0
TMC0
Free running mode
(b) Capture/compare control register 0 (CRC0)
0
0
0
0
0
CRC02
1
CRC01
0/1
CRC00
0
CRC0
CR00 as compare register
CR01 as capture register
Remark
0/1:
When these bits are reset to 0 or set to 1, the other functions can be used along with the pulse
width measurement function. For details, refer to
Figures 8-2
and
8-3
.
