UPD78F9500MA-CAC-A Datasheet, PDF (114/342 Pages) Renesas Technology Corp – 8-Bit Single-Chip Microcontrollers

CHAPTER 6 16-BIT TIMER/EVENT COUNTER 00 (μPD78F920x ONLY)
Figure 6-25. Timing of Pulse Width Measurement Operation by Free-Running Counter
and Two Capture Registers (with Rising Edge Specified)
t
Count clock
TM00 count value
TI000 pin input
CR010 capture value
CR000 capture value
INTTM010
0000H 0001H
D0 D0 + 1
D0
D1 D1 + 1
FFFFH 0000H
D1
D2 D2 + 1
D2
D3
D3
(D1 − D0) × t
(D2 − D1) × t ^Note
(D3 − D2) × t
Note The carry flag is set to 1. Ignore this setting.
(4) Pulse width measurement by means of restart
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 input of a valid edge to the TI000 pin is detected, the count value of 16-bit timer/counter 00 (TM00) is
taken into 16-bit timer capture/compare register 010 (CR010), and then the pulse width of the signal input to
the TI000 pin is measured by clearing TM00 and restarting the count.
The edge specification can be selected from two types, rising or falling edges, by bits 4 and 5 (ES000 and
ES010) of prescaler mode register 00 (PRM00)
Sampling is performed at the interval 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.
Figure 6-26. Control Register Settings for Pulse Width Measurement by Means of Restart
(with Rising Edge Specified) (1/2)
(a) Capture/compare control register 00 (CRC00)
7
6
5
4
3 CRC002 CRC001 CRC000
CRC00 0
0
0
0
0
1
1
1
CR000 used as capture register
Captures to CR000 at inverse edge to valid edge of TI000^Note.
CR010 used as capture register
Note If the valid edge of TI000 is specified to be both the rising and falling edges, 16-bit timer capture/compare
register 000 (CR000) cannot perform the capture operation.
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User’s Manual U18172EJ3V0UD