R27 datasheet(185/487 Pages) RENESAS

185 / 487 page

R8C/26 Group, R8C/27 Group

14. Timers

Rev.2.10

Sep 26, 2008

Page 166 of 453

REJ09B0278-0210

14.2.2

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

14.8 Specifications of Programmable Waveform Generation Mode). Counting starts by counting the setting

value in the TRBPR register. The TRBOCR register is unused in this mode.

Figure 14.18 shows the TRBIOC Register in Programmable Waveform Generation Mode. Figure 14.19 shows

an Operating Example of Timer RB in Programmable Waveform Generation 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 14.8

Specifications of Programmable Waveform Generation Mode

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)

Select functions

• Output level select function

The TOPL bit in the TRBIOC register selects the output level during primary

and secondary periods.

• TRBO pin output switch function

Timer RB pulse output or P3_1 (P1_3) latch output is selected by the

TOCNT bit in the TRBIOC register.(3)

• TRBO pin select function

P3_1 or P1_3 is selected by the TRBOSEL bit in the PINSR2 register.

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