
CHAPTER 6 16-BIT TIMER/EVENT COUNTERS 00 AND 01
Preliminary User’s Manual U16228EJ1V0UD
171
(3) Pulse width measurement with free-running counter and two capture registers
When 16-bit timer counter 0n (TM0n) is operated in free-running mode (see Figure 6-24), it is possible to
measure the pulse width of the signal input to the TI00n pin.
When the edge specified by bits 4 and 5 (ES0n0 and ES0n1) of prescaler mode register 0n (PRM0n) is input to
the TI00n pin, the value of TM0n is taken into 16-bit timer capture/compare register 01n (CR01n) and an interrupt
request signal (INTTM01n) is set.
Also, when the inverse edge to that of the capture operation is input into CR01n, the value of TM0n is taken into
16-bit timer capture/compare register 00n (CR00n).
Either of two edges
rising or fallingcan be selected as the valid edge of the TI00n pin specified using bits 4
and 5 (ES0n0 and ES0n1) of prescaler mode register 0n (PRM0n).
For TI00n pin valid edge detection, sampling is performed at the interval selected by prescaler mode register 0n
(PRM0n), and a capture operation is only performed when a valid level is detected twice, thus eliminating noise
with a short pulse width.
Figure 6-24. Control Register Settings for Pulse Width Measurement with Free-Running Counter and
Two Capture Registers
(a) 16-bit timer mode control register 0n (TMC0n)
0000
TMC0n3
0
TMC0n2
1
TMC0n1
0/1
OVF0n
0
TMC0n
Free-running mode
(b) Capture/compare control register 0n (CRC0n)
00000
CRC0n2
1
CRC0n1
1
CRC0n0
1
CRC0n
CR00n used as capture register
Captures to CR00n at inverse edge
to valid edge of TI00n.
CR01n used as capture register
Remark
0/1: Setting 0 or 1 allows another function to be used simultaneously with pulse width measurement.
See the description of the respective control registers for details.
n = 0:
PD780131, 780132
n = 0, 1:
PD780133, 780134, 78F0134, 780136, 780138, 78F0138