R8CSLASH20 datasheet(144/501 Pages) RENESAS

144 / 501 page

R8C/20 Group, R8C/21 Group

14. Timers

Rev.2.00 Aug 27, 2008

Page 128 of 458

REJ09B0250-0200

14.1.3

Event Counter Mode

Event counter mode is mode to count an external signal which inputs from the INT1/TRAIO pin (see Table

14.4 Event Counter Mode Specifications).

Figure 14.8 shows the TRAIOC Register in Event Counter Mode.

NOTE:

1. The level of output pulse turn into the level when the pulse output starts by writing the TRAMR

Table 14.4

Event Counter Mode Specifications

Item

Specification

Count Source

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

program)

Count Operations

• Decrement

• When the timer underflows, the contents in the reload register is reloaded and

the count is inherited

Divide Ratio

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

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

Count Start Condition

Write 1 (count starts) to the TSTART bit in the TRACR register

Count Stop

Conditions

• Write 0 (count stops) to the TSTART bit in the TRACR register

• Write 1 (count forcibly stops) 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(1)

Read from Timer

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

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 can select 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

The pulse which inverts the polarity can be output from the TRAO pin each time

the timer underflows. (selected 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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