Renesas R8C/20 User Manual

R8C/20 Group, R8C/21 Group 14. Timers
Rev.2.00 Aug 27, 2008 Page 141 of 458
REJ09B0250-0200
14.2.1 Timer Mode
Timer mode is mode to count a count source which is internally generated or timer RA underflow (see Table
14.7 Timer Mode Specifications). The TRBOCR and TRBSC registers are unused in timer mode.
Figure 14.17 shows the TRBIOC Register in Timer Mode.
Figure 14.17 TRBIOC Register in Timer Mode
Table 14.7 Timer Mode Specifications
Item Specification
Count Sources f1, f2, f8, Timer RA underflow
Count Operations • Decrement
• When the timer underflows, it reloads the reload register contents before the
count continues (when timer RB underflows, the contents of timer RB primary
reload register is reloaded)
Divide Ratio 1/(n+1)(m+1)
n: setting value in TRBPRE register, m: setting value in TRBPR register
Count Start Condition Write 1 (count starts) to the TSTART bit in the TRBCR register
Count Stop Conditions • Write 0 (count stops) to the TSTART bit in the TRBCR register
• Write 1 (count forcibly stop) to the TSTOP bit in the TRBCR register
Interrupt Request
Generation Timing
When timer RB underflows [timer RB interrupt]
TRBO Pin Function Programmable I/O port
INT0
Pin Function Programmable I/O port or INT0 interrupt input
Read from Timer The count value can be read out by reading the TRBPR and TRBPRE registers
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 to while count operation is in
progress:
If the TWRC bit in the TRBMR register is set to 0, the value is written to both
the reload register and the counter.
If the TWRC bit is set to 1, the value is written to the reload register only.
(Refer to 14.2.1.1 Timer Write Control during Count Operation.)
Timer RB I/O Control Registe
r
Symbol Address After Reset
TRBIOC
010Ah 00h
Bit Symbol Bit Name Function RW
0
TOPL
Timer RB output level select
bit
Timer RB output sw itch bit
b7 b6 b5 b4 b3 b2
INOSEG
b1 b0
00
INOSTG
TOCNT
0
Nothing is assigned. If necessary, set to 0.
When read, the content is 0.
One-shot trigger polarity
select bit
—
(b7-b4)
—
Set to 0 in timer mode
RW
RW
RW
RW
One-shot trigger control bit

Renesas R8C/20 Specifications

General

Brand	Renesas
Model	R8C/20
Category	Control Unit
Language	English