Datasheet

78K0/Ix2 CHAPTER 7 16-BIT TIMER/EVENT COUNTER 00
R01UH0010EJ0500 Rev.5.00 310
Feb 28, 2012
(2) Measuring the pulse width by using one input signal of the TI000 pin (free-running timer mode)
Set the free-running timer mode (TMC003 and TMC002 = 01). The count value of TM00 is captured to CR000 in the
phase reverse to the valid edge detected on the TI000 pin. When the valid edge of the TI000 pin is detected, the
count value of TM00 is captured to CR010.
By this measurement method, values are stored in separate capture registers when a width from one edge to another
is measured. Therefore, the capture values do not have to be saved. By subtracting the value of one capture register
from that of another, a high-level width, low-level width, and cycle are calculated.
If an overflow occurs, the value becomes negative if one captured value is simply subtracted from another and,
therefore, a borrow occurs (bit 0 (CY) of the program status word (PSW) is set to 1). If this happens, ignore CY and
take the calculated value as the pulse width. In addition, clear bit 0 (OVF00) of 16-bit timer mode control register 00
(TMC00) to 0.
Figure 7-50. Timing Example of Pulse Width Measurement (2)
 TMC00 = 04H, PRM00 = 10H, CRC00 = 07H
FFFFH
TM00 register
0000H
Operable bits
(TMC003, TMC002)
Capture trigger input
(TI000)
Capture register
(CR000)
Capture register
(CR010)
Capture interrupt
(INTTM010)
Overflow flag
(OVF00)
Capture trigger input
(TI010)
Capture interrupt
(INTTM000)
01
M
A
B
C
DE
N
S
P
Q
00
0 write clear 0 write clear 0 write clear 0 write clear
0000H
L
L
ABC
D
E
0000H
MN S
P
Q