
R8C/3GM Group
18. Timer RB
R01UH0284EJ0100 Rev.1.00
Aug 09, 2011
18.6
Programmable Wait One-Shot Generation Mode
In programmable wait one-shot generation mode, a one-shot pulse is output from the TRBO pin by a program or an
Mode Specifications). When a trigger is generated from that point, the timer outputs a pulse only once for a given
length of time equal to the setting value in the TRBSC register after waiting for a given length of time equal to the
setting value in the TRBPR register.
Note:
1. The set value is reflected at the following one-shot pulse after writing to registers TRBSC and TRBPR.
Table 18.5
Programmable Wait One-Shot Generation Mode Specifications
Item
Specification
Count sources
f1, f2, f8, timer RA underflow
Count operations
Decrement the timer RB primary setting value.
When a count of the timer RB primary underflows, the timer reloads the contents of
timer RB secondary before the count continues.
When a count of the timer RB secondary underflows, the timer reloads the contents
of timer RB primary before the count completes and the TOSSTF bit is set to 0
(one-shot stops).
When the count stops, the timer reloads the contents of the reload register before it
stops.
Wait time
(n+1)(m+1)/fi
fi: Count source frequency
n: Value set in the TRBPRE register, m Value set in the TRBPR register
One-shot pulse output time
(n+1)(p+1)/fi
fi: Count source frequency
n: Value set in the TRBPRE register, p: Value set in the TRBSC register
Count start conditions
The TSTART bit in the TRBCR register is set to 1 (count starts) and the next trigger
is generated.
Set the TOSST bit in the TRBOCR register to 1 (one-shot starts).
Input trigger to the INT0 pin
Count stop conditions
When reloading completes after timer RB underflows during secondary period.
When the TOSSP bit in the TRBOCR register is set to 1 (one-shot stops).
When the TSTART bit in the TRBCR register is set to 0 (starts counting).
When the TSTOP bit in the TRBCR register is set to 1 (forcibly stops counting).
Interrupt request generation
timing
In half a cycle of the count source after timer RB underflows during secondary period
(complete at the same time as waveform output from the TRBO pin) [timer RB
interrupt].
TRBO pin function
Pulse output
INT0 pin functions
When the INOSTG bit in the TRBIOC register is set to 0 (INT0 one-shot trigger
disabled): programmable I/O port or INT0 interrupt input
When the INOSTG bit in the TRBIOC register is set to 1 (INT0 one-shot trigger
enabled): external trigger (INT0 interrupt input)
Read from timer
The count value can be read out by reading registers TRBPR and TRBPRE.
Write to timer
When registers TRBPRE, TRBSC, and TRBPR are written while the count stops,
values are written to both the reload register and counter.
When registers TRBPRE, TRBSC, and TRBPR are written to during count
operation, values are written to the reload registers only.
(1)Selectable functions
Output level select function
The output level of the one-shot pulse waveform is selected by the TOPL bit in the
TRBIOC register.
One-shot trigger select function