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R8C/18 Group, R8C/19 Group
14.1.5
Pulse Period Measurement Mode
In pulse period measurement mode, the pulse period of an external signal input to the INT1/CNTR0
pin is measured (refer to Table 14.6 Pulse Period Measurement Mode Specifications). Figure 14.9
shows the TXMR Register in Pulse Period Measurement Mode. Figure 14.10 shows an Operating
Example in Pulse Period Measurement Mode.
Table 14.6
Pulse Period Measurement Mode Specifications
Item
Count sources
Count operations
Count start condition
Count stop condition
Interrupt request
generation timing
INT10/CNTR00,
INT11/CNTR01
pin functions
CNTR0 pin function
Read from timer
Write to timer
Select functions
NOTE:
1. Input a pulse with a period longer than twice of the prescaler X period. Input a pulse with a longer
"H" and "L" width than the prescaler X period. If a pulse with a shorter period is input to the CNTR0
pin, the input may be ignored.
Rev.1.30
Apr 14, 2006
REJ09B0222-0130
f1, f2, f8, fRING
• Decrement
• After an active edge of the measured 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.
1 (count starts) is written to the TXS bit in the TXMR register.
0 (count stops) is written to the TXS bit in the TXMR register.
• When timer X underflows or reloads [timer X interrupt].
• Rising or falling of CNTR0 input (end of measurement period) [INT1 interrupt]
Measured pulse input
Programmable I/O port
Contents of the read-out buffer can be read out by reading the TX register. The
value retained in the read-out buffer is released by reading the TX register.
• When registers TX and PREX are written while the count is stopped, values
are written to both the reload register and counter.
• When registers TX and PREX are written during the count, the value is
written to each reload register of registers TX and PREX at the following
count source input, the data is transferred to the counter at the second count
source input, and the count re-starts at the third count source input.
• INT1/CNTR0 polarity switch function
The R0EDG bit can select the measurement period for the input pulse.
• Measured pulse input pin select function
The CNTRSEL bit in the UCON register can select the CNTR00 or CNTR01
pin.
Page 113 of 233
Specification
(1)
(INT1 interrupt input)
14. Timers
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