NEC 78K0S/KB1+ User Manual page 105

Figure 6-22. Timing of Pulse Width Measurement Operation with Free-Running Counter
(with Both Edges Specified)
t
Count clock
0000H
TM00 count value
TI000 pin input
CR010 capture value
INTTM010
TI010 pin input
CR000 capture value
INTTM000
Note The carry flag is set to 1. Ignore this setting.
(3) Pulse width measurement with free-running counter and two capture registers
When 16-bit timer counter 00 (TM00) is operated in free-running mode, it is possible to measure the pulse
width of the signal input to the TI000 pin.
When the rising or falling edge specified by bits 4 and 5 (ES000 and ES010) of prescaler mode register 00
(PRM00) is input to the TI000 pin, the value of TM00 is taken into 16-bit timer capture/compare register 010
(CR010) and an interrupt request signal (INTTM010) is set.
Also, when the inverse edge to that of the capture operation is input into CR010, the value of TM00 is taken
into 16-bit timer capture/compare register 000 (CR000).
Sampling is performed using the count clock cycle selected by prescaler mode register 00 (PRM00), and a
capture operation is only performed when a valid level of the TI000 pin is detected twice, thus eliminating
noise with a short pulse width.
Caution The measurable pulse width in this operation example is up to 1 cycle of the timer counter.
CHAPTER 6 16-BIT TIMER/EVENT COUNTER 00
0001H D0 D0 + 1
D0
(D1 − D0) × t
User's Manual U17446EJ3V1UD
D1 D1 + 1 FFFFH 0000H
D1
D1
(D2 − D1) × t Note
((D2 + 1) − D1) × t
Note
D2 D2 + 1 D2 + 2 D3
D2
D2 + 1
(D3 − D2) × t
105