
R8C/14 Group, R8C/15 Group 13. Timers
Rev.2.10 Jan 19, 2006 Page 97 of 253
REJ09B0164-0210
Figure 13.10 Operating Example in Pulse Period Measurement Mode
Underflow Signal of
Prescaler X
NOTES :
1. The contents of the read-out buffer can be read when the TX register is read in pulse period measurement mode.
2. After an active edge of measurement pulse is input, the TXEDG bit in the TXMR register is set to “1” (active edge found)
when the prescale X underflows for the second time.
3. The TX register should be read before the next active edge is input after the TXEDG bit is set to “1” (active edge found).
The contents in the read-out buffer is retained until the TX register is read. If the TX register is not read before the next
active edge is input, the measured result of the previous period is retained.
4. When set to “0” by program, use a MOV instruction to write “0” to the TXEDG in the TXMR register. At the same time,
write “1” to the TXUND bit.
5. When set to “0” by program, use a MOV instruction to write “0” to the TXUND in the TXMR register. At the same time,
write “1” to the TXEDG bit.
6. The TXUND and TXEDG bits are both set to “1” if the timer underflows and reloads on an active edge simultaneously.
In this case, the validity of the TXUND bit should be determined by the contents of the read-out buffer.
7. If the CNTR0 active edge is input, when the prescaler X underflow signal is “H” level, its count value is the one of the
read buffer. If “L” level, the following count value is the one of the read buffer.
0Fh 0Eh 0Dh 0Ch 0Bh 0Ah 09h 08h 0Fh 0Eh 0Dh 01h 00h 0Fh 0Eh0Fh
0Eh
0Fh 0Ah 0Dh 01h 0Fh 0Eh08h
TXS Bit in TXMR
Register
TXEDG Bit in
TXMR Register
“1”
“0”
CNTR0i Pin Input
Contents of Timer X
Contents of
Read-Out Buffer1
IR Bit in
TXIC Register
IR Bit in INT1IC
Register
TXUND Bit in
TXMR Register
Set to “1” by program
Starts
counting
Timer X
reloads
Retained
Timer X read
(3)
Retained
(7)
Set to “0” by program
(4)
(2) (2)
(6)
(7)
Timer X read
(3)
Timer X
reloads
Timer X
reloads
Set to “0” by program
(5)
Set to “0” when interrupt request is acknowledged, or set by program
Set to “0” when interrupt request is acknowledged, or set by program
“1”
“0”
“1”
“0”
“1”
“0”
“1”
“0”
“1”
“0”
00h09h
0Eh
Conditions: A period from one rising edge to the next rising edge of measurement pulse is measured (R0EDG=0)
with the default value of the TX register as 0Fh.
i=0 to 1
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