Pulse Width Measurement Operations - NEC mPD780024AS Series Preliminary User's Manual

6.4.3 Pulse width measurement operations

It is possible to measure the pulse width of the signals input to the TI00/TO0/P70 pin and TI01/P71 pin using the
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/TO0/P70 pin.
(1) Pulse width measurement with free-running counter and one capture register
When the 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/TO0/P70 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 edge can be selected—rising, falling, or both edges—specified by means of bits 4 and 5 (ES00 and
ES01) of PRM0.
For valid edge detection, sampling is performed at the count clock selected by PRM0, and a capture operation
is only performed when a valid level 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
TMC0
CRC0
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.
CHAPTER 6 16-BIT TIMER/EVENT COUNTER 0
(a) 16-bit timer mode control register 0 (TMC0)
TMC03
0 0 0 0 0
(b) Capture/compare control register 0 (CRC0)
0 0 0 0 0
Preliminary User's Manual U16035EJ1V0UM
TMC02 TMC01 OVF0
1 0/1 0
Free-running mode
CRC02 CRC01 CRC00
1 0/1 0
CR00 as compare register
CR01 as capture register
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