
R8C/3GM Group
18. Timer RB
R01UH0284EJ0100 Rev.1.00
Aug 09, 2011
18.5
Programmable One-shot Generation Mode
In programmable one-shot generation mode, a one-shot pulse is output from the TRBO pin by a program or an
Specifications). When a trigger is generated, the timer starts operating from the point only once for a given period
equal to the set value in the TRBPR register. The TRBSC register is not used in this mode.
Note:
1. The set value is reflected at the following one-shot pulse after writing to the TRBPR register.
Table 18.4
Programmable One-Shot Generation Mode Specifications
Item
Specification
Count sources
f1, f2, f8, timer RA underflow
Count operations
Decrement the setting value in the TRBPR register
When the timer underflows, it reloads the contents of the reload register 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.
One-shot pulse
output time
(n+1)(m+1)/fi
fi: Count source frequency,
n: Setting value in TRBPRE register, m: Setting value in TRBPR 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 primary 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 (stops 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 the timer underflows (at the same time as
the TRBO output ends) [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 and TRBPR are written while the count is stopped,
values are written to both the reload register and counter.
When registers TRBPRE and TRBPR are written during the count, values are
written to the reload register only (the data is transferred to the counter at the
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