R29 datasheet(162/473 Pages) RENESAS

162 / 473 page

R8C/28 Group, R8C/29 Group

14. Timers

Rev.2.10

Sep 26, 2008

Page 143 of 441

REJ09B0279-0210

14.1.3

Event Counter Mode

In event counter mode, external signal inputs to the INT1/TRAIO pin are counted (refer to Table 14.4

Specifications of Event Counter Mode).

Figure 14.7 shows the TRAIOC Register in Event Counter Mode.

NOTE:

1. The level of the output pulse becomes the level when the pulse output starts when the TRAMR

Table 14.4

Specifications of Event Counter Mode

Item

Specification

Count source

External signal which is input to TRAIO pin (active edge selectable by a

program)

Count operations

• Decrement

• When the timer underflows, the contents of the reload register are reloaded

and the count is continued.

Divide ratio

1/(n+1)(m+1)

n: setting value of TRAPRE register, m: setting value of TRA register

Count start condition

1 (count starts) is written to the TSTART bit in the TRACR register.

Count stop conditions

• 0 (count stops) is written to the TSTART bit in the TRACR register.

• 1 (count forcibly stops) is written to the TSTOP bit in the TRACR register.

Interrupt request

generation timing

• When timer RA underflows [timer RA interrupt].

INT1/TRAIO pin function Count source input (INT1 interrupt input)

TRAO pin function

Programmable I/O port or pulse output(1)

Read from timer

The count value can be read by reading registers TRA and TRAPRE.

Write to timer

• When registers TRAPRE and TRA are written while the count is stopped,

values are written to both the reload register and counter.

• When registers TRAPRE and TRA are written during the count, values are

written to the reload register and counter (refer to 14.1.1.1 Timer Write

Control during Count Operation).

Select functions

•INT1 input polarity switch function

The TEDGSEL bit in the TRAIOC register selects the active edge of the

count source.

• Count source input pin select function

P1_7 or P1_5 is selected by the TIOSEL bit in the TRAIOC register.

• Pulse output function

Pulses of inverted polarity can be output from the TRAO pin each time the

timer underflows (selectable by the TOENA bit in the TRAIOC register).(1)

• Digital filter function

Bits TIPF0 and TIPF1 in the TRAIOC register enable or disable the digital

filter and select the sampling frequency.

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