R8CSLASH2G datasheet(179/344 Pages) RENESAS

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R8C/2G Group

17. Timers

Rev.1.00

Apr 04, 2008

Page 159 of 318

REJ09B0387-0100

Figure 17.11

Operating Example of Pulse Period Measurement Mode

Underflow signal of

timer RA prescaler

NOTES:

1. The contents of the read-out buffer can be read by reading the TRA register in pulse period measurement mode.

2. After an active edge of the measured pulse is input, the TEDGF bit in the TRACR register is set to 1 (active edge found) when the timer

RA prescaler underflows for the second time.

3. The TRA register should be read before the next active edge is input after the TEDGF bit is set to 1 (active edge found).

The contents in the read-out buffer are retained until the TRA register is read. If the TRA register is not read before the next active edge

is input, the measured result of the previous period is retained.

4. To set to 0 by a program, use a MOV instruction to write 0 to the TEDGF bit in the TRACR register. At the same time, write 1 to the

TUNDF bit in the TRACR register.

5. To set to 0 by a program, use a MOV instruction to write 0 to the TUNDF bit. At the same time, write 1 to the TEDGF bit.

6. Bits TUNDF and TEDGF are both set to 1 if timer RA underflows and reloads on an active edge simultaneously.

0Eh 0Dh 0Fh 0Eh 0Dh 0Ch 0Bh 0Ah 09h 0Fh 0Eh 0Dh

01h 00h 0Fh 0Eh

0Fh

0Dh

0Fh

0Bh 0Ah

0Dh

01h 00h 0Fh 0Eh

09h

TSTART bit in

TRACR register

TEDGF bit in

TRACR register

Measurement pulse

(TRAIO pin input)

Contents of TRA

Contents of read-out

buffer(1)

IR bit in TRAIC

TUNDF bit in

TRACR register

Set to 1 by program

Starts counting

TRA reloads

TRA read(3)

Retained

(Note 2)

Set to 0 by program

Conditions: The period from one rising edge to the next rising edge of the measured pulse is measured (TEDGSEL = 0) with

the default value of the TRA register as 0Fh.

0Eh

TRA reloads

Retained

Set to 0 when interrupt request is acknowledged, or set by program

Set to 0 by program

Underflow

(Note 2)

(Note 4)

(Note 6)

(Note 5)

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