R29 datasheet(181/473 Pages) RENESAS

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R8C/28 Group, R8C/29 Group

14. Timers

Rev.2.10

Sep 26, 2008

Page 162 of 441

REJ09B0279-0210

14.2.3

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

external trigger input (input to the INT0 pin) (refer to Table 14.9 Specifications of Programmable One-Shot

Generation Mode). 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.

Figure 14.20 shows the TRBIOC Register in Programmable One-Shot Generation Mode. Figure 14.21 shows

an Operating Example of Programmable One-Shot Generation Mode.

NOTES:

1. The set value is reflected at the following one-shot pulse after writing to the TRBPR register.

2. Do not set both the TRBPRE and TRBPR registers to 00h.

3. Set the TRBOSEL bit in the PINSR2 register to 1 (enabled) before using timer RB.

Refer to 7. Programmable I/O Ports for details.

Table 14.9

Specifications of Programmable One-Shot Generation Mode

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(2)

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(3)

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

following reload).(1)

Select functions

• Output level select function

The TOPL bit in the TRBIOC register selects the output level of the one-shot

pulse waveform.

• One-shot trigger select function

Refer to 14.2.3.1 One-Shot Trigger Selection.

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