R8C/20 Group, R8C/21 Group 14. Timers
Rev.2.00 Aug 27, 2008 Page 137 of 458
REJ09B0250-0200
14.2 Timer RB
Timer RB is an 8-bit timer with an 8-bit prescaler.
The prescaler and timer consist of the reload register and counter. (Refer to Table 14.7 to 14.10 the Specification
of Each Modes).
Timer RB contains the timer RB primary and timer RB secondary as the reload register.
The count source for timer RB is the operating clock that regulates the timing of timer operations such as counting
and reloading.
Figure 14.13 shows the Block Diagram of Timer RB. Figures 14.14 and 14.16 show the registers associated with
timer RB.
Timer RB contains four operation modes listed as follows:
• Timer mode: The timer counts an internal count source (peripheral function
clock or timer RA underflows).
• Programmable waveform generation mode: The timer outputs pulses of a given width successively.
• Programmable one-shot generation mode: The timer outputs one-shot pulse.
• Programmable wait one-shot generation mode: The timer outputs delayed one-shot pulse.
Figure 14.13 Block Diagram of Timer RB
INT0PL bit
= 00b
= 01b
= 11b
f8
f1
= 10b
Timer RA underflow
TCK1 to TCK0 bit
TSTART bit
TRBPRE register
(Prescaler)
Timer RB interrupt
INT0 interrupt
TCSTF bit
Toggle flip-flop
Q
Q
CLR
CK
TOPL = 1
TOPL = 0
TRBO pin
TOCNT = 0
TOCNT = 1
P3_1 bit in P3 register
f2
TMOD1 to TMOD0 bit
= 10b or 11b
TOSSTF bit
Polarity
select
INOSEG bit
Input polarity
selected to be one
edge or both edges
Digital filter
INT0 pin
INT0EN bit
TMOD1 to TMOD0 bit
= 01b
, 10b, 11b
TMOD1 to TMOD0 bit
= 01b
, 10b, 11b
Counter
Reload
register
Counter (timer RB)
Reload
register
TRBPR
register
Peripheral data bus
TRBSC
register
Reload
register
TCKCUT bit
INOSTG bit
TSTART, TCSTF: TRBCR register
TOSST: TRBOCR register
TOPL, TOCNT, INOSTG, INOSEG: TRBIOC register
TMOD1 to TMOD0, TCK1 to TCK0, TCKCUT: TRBMR register
(Timer)
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