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CHAPTER 6 16-BIT TIMER/EVENT COUNTER 0
User
’
s Manual U14701EJ3V0UD
6.5.3 Pulse width measurement operations
It is possible to measure the pulse width of the signals input to the TI00/P31 pin and TI01/P32 pin using
16-bit timer counter 0 (TM0).
There are two measurement methods: measuring with TM0 used in free-running mode, and measuring by restarting
the timer in synchronization with the edge of the signal input to the TI00/P31 pin.
(1) Pulse width measurement with free-running counter and one capture register
When 16-bit timer counter 0 (TM0) is operated in free-running mode (see register settings in
Figure 6-11
), and
the edge specified by prescaler mode register 0 (PRM0) is input to the TI00/P31 pin, the value of TM0 is taken
into 16-bit timer capture/compare register 01 (CR01) and an external interrupt request signal (INTTM01) is set.
Any of three edges can be selected
—
rising, falling, or both edges
—
specified by means of bits 4 and 5 (ES00
and ES01) of PRM0.
Sampling is performed at the count clock selected by PRM0, and a capture operation is only performed when
a valid level of the TI00/P31 pin or TI01/P32 pin is detected twice, thus eliminating noise with a short pulse width.
Figure 6-11. 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: Setting 0 or 1 allows another function to be used simultaneously with pulse width measurement.
See
Figures
6-2
and
6-3
.