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R8C/20 Group, R8C/21 Group 14. Timers

Rev.2.00 Aug 27, 2008 Page 130 of 458

REJ09B0250-0200

14.1.4 Pulse Width Measurement Mode

Pulse width measurement mode is mode to measure the pulse width of an external signal which inputs from the

INT1

/TRAIO pin (see Table 14.5 Pulse Width Measurement Mode Specifications).

Figure 14.9 shows the TRAIOC Register in Pulse Width Measurement Mode and Figure 14.10 shows the

Operating Example of Pulse Width Measurement Mode.

Table 14.5 Pulse Width Measurement Mode Specifications

Item Specification

Count Sources f1, f2, f8, fOCO

Count Operations • Decrement

• Continuously counts the selected signal only when measurement pulse is “H”

level, or conversely only “L” level.

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

and the count is inherited

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]

• Rising or falling of the TRAIO input (end of measurement period) [timer RA

interrupt]

INT1

/TRAIO Pin

Function

Measurement pulse input (INT1 interrupt input)

TRAO Pin Function

Programmable I/O port

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

• Measurement level select

The TEDGSEL bit in the TRAIOC register can select during “H” or “L” level

Renesas R8C/20 User Manual

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