Pulse Width Measurement Operations - NEC mPD780208 Subseries User Manual

Figure 6-13 shows an example in which PWM output is converted to an analog voltage and used in a voltage
synthesizer type TV tuner.
µ
PD780205
TO0/P30
V
SS

6.5.3 Pulse width measurement operations

It is possible to measure the pulse width of the signals input to the TI0/P00 pin using the 16-bit timer register (TM0).
There are two measurement methods: measuring with the 16-bit timer register (TM0) used in free-running mode,
and measuring by restarting the timer in synchronization with the valid edge of the signal input to the TI0/P00 pin.
(1) Pulse width measurement in free-running mode
When the 16-bit timer register (TM0) is operated in free-running mode, if the edge specified by the external
interrupt mode register (INTM0) is input, the value of TM0 is taken into the capture register (CR01) and an external
interrupt request signal (INTP0) is set.
Any of three edge specifications can be selected—rising, falling, or both edges—by using bits 2 and 3 (ES10
and ES11) of INTM0.
For valid edge detection, sampling is performed at the interval selected by the sampling clock select register
(SCS), and a capture operation is only performed when a valid level is detected twice, thus eliminating noise with
a short pulse width.
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CHAPTER 6 16-BIT TIMER/EVENT COUNTER
Figure 6-13. TV Tuner Application Circuit Example
+110 V
22 kΩ
47 kΩ
100 pF
8.2 kΩ
8.2 kΩ
User's Manual U11302EJ4V0UM
47 kΩ 47 kΩ
µ µ
µ
0.22 F 0.22 F 0.22 F
Electronic
tuner
GND