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R8C/14 Group, R8C/15 Group 13. Timers
Rev.2.10 Jan 19, 2006 Page 95 of 253
REJ09B0164-0210
13.1.5 Pulse Period Measurement Mode
Pulse period measurement mode is mode to measure the pulse period of an external signal which
inputs from the INT1
/CNTR0 pin (See Table 13.6 Specification of Pulse Period Measurement
Mode). Figure 13.9 shows the TXMR Register in Pulse Period Measurement Mode. Figure 13.10
shows an Operating Example in Pulse Period Measurement Mode.
NOTES:
1. Input the pulse whose period is longer than twice of the prescaler X period. Input the longer pulse for
“H” width and “L” width than the prescaler X period. If the shorter pulse than the period is input to the
CNTR0 pin, the input may be disabled.
Table 13.6 Specification of Pulse Period Measurement Mode
Item Specification
Count Source f1, f2, f8, fRING
Count Operation Decrement
After an active edge of measurement pulse is input, contents for the read-out
buffer are retained at the first underflow of prescaler X. Then timer X reloads
contents in the reload register at the second underflow of prescaler X and
continues counting.
Count Start Condition Write “1” (count start) to the TXS bit in the TXMR register
Count Stop Condition Write “0” (count stop) to TXS bit in TXMR register
Interrupt Request
Generation Timing
When timer X underflows or reloads [timer X interrupt]
Rising or falling of CNTR0 input (end of measurement period) [INT1
interrupt]
INT10
/CNTR00,
INT11
/CNTR01 Pin
Function
Measurement pulse input
(1)
(INT1 interrupt input)
CNTR0
Pin Function
Programmable I/O port
Read from Timer Contents in the read-out buffer can be read by reading the TX register. The
value retained in the read-out buffer is released by reading TX register.
Write to Timer When writing to the TX and PREX registers while the count stops, the value
is written to both the reload register and counter.
When writing to the TX and PREX registers during the count, the value is
written to each reload register of the TX and PREX registers at the following
count source input and the data is transferred to the counter at the second
count source input and the count re-starts at the third count source input.
Select Function
•INT1
/CNTR0 polarity switch function
The R0EDG bit can select the measurement period of input pulse.
Measurement pulse input pin select function
The CNTRSEL bit in the UCON register can select the CNTR00 or CNTR01
pin.
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