Datasheet

CHAPTER 6 16-BIT TIMER/EVENT COUNTER 00 ( μ PD78F920x ONLY)
User’s Manual U18172EJ3V0UD
110
Figure 6-23. Timing of Pulse Width Measurement Operation with Free-Running Counter
(with Both Edges Specified)
t
0000H 0000H FFFFH 0001H D0
D0
(D1 − D0) × t (D3 − D2) × t(D2 − D1) × t
((D2 + 1) − D1) × t
D1
D2 + 1D1
D2
D2 D3
D0 + 1 D1 D1 + 1 D2 + 1 D2 + 2
Note
TI010 pin input
CR000 capture value
INTTM010
INTTM000
Count clock
TM00 count value
TI000 pin input
CR010 capture value
Note
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.
Specify both the rising and falling edges as the valid edges of the TI000 pin, by using bits 4 and 5 (ES000 and
ES010) of PRM00.
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.