
R8C/3GM Group
18. Timer RB
R01UH0284EJ0100 Rev.1.00
Aug 09, 2011
18.4
Programmable Waveform Generation Mode
In programmable waveform generation mode, the signal output from the TRBO pin is inverted each time the
counter underflows, while the values in registers TRBPR and TRBSC are counted alternately (refer to
Table 18.3TRBPR register. The TRBOCR register is unused in this mode.
Notes:
1. Even when counting the secondary period, the TRBPR register may be read.
2. The set values are reflected in the waveform output beginning with the following primary period after writing to
the TRBPR register.
3. The value written to the TOCNT bit is enabled by the following.
When counting starts.
When a timer RB interrupt request is generated.
The contents after the TOCNT bit is changed are reflected from the output of the following primary period.
Table 18.3
Programmable Waveform Generation Mode Specifications
Item
Specification
Count sources
f1, f2, f8, timer RA underflow
Count operations
Decrement
When the timer underflows, it reloads the contents of the primary reload and secondary
reload registers alternately before the count continues.
Width and period of
output waveform
Primary period: (n+1)(m+1)/fi
Secondary period: (n+1)(p+1)/fi
Period: (n+1){(m+1)+(p+1)}/fi
fi: Count source frequency
n: Value set in TRBPRE register, m: Value set in TRBPR register
p: Value set in TRBSC register
Count start condition
1 (count start) is written to the TSTART bit in the TRBCR register.
Count stop conditions
0 (count stop) is written to the TSTART bit in the TRBCR register.
1 (count forcibly stop) is written to the TSTOP bit in the TRBCR register.
Interrupt request
generation timing
In half a cycle of the count source, after timer RB underflows during the secondary period
(at the same time as the TRBO output change) [timer RB interrupt]
TRBO pin function
Programmable output port or pulse output
INT0 pin function
Programmable I/O port or INT0 interrupt input
Read from timer
The count value can be read out by reading registers TRBPR and TRBPRE
(1).Write to timer
When registers TRBPRE, TRBSC, and TRBPR are written while the count is stopped,
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.
(2)Selectable functions
Output level select function
The output level during primary and secondary periods is selected by the TOPL bit in the
TRBIOC register.
TRBO pin output switch function
Timer RB pulse output or P1_3 latch output is selected by the TOCNT bit in the TRBIOC