R8C datasheet(71/199 Pages) RENESAS

71 / 199 page

R8C/10 Group

Rev.1.20 Jan 27, 2006

page 61 of 180

REJ09B0019-0120

12.1.4 Pulse Width Measurement Mode

_____

In this mode, the timer measures the pulse width of an external signal fed to INT1/CNTR0 pin (See

“Table 12.5 Pulse Width Measurement Mode Specifications”). Figure 12.7 shows the TXMR register

in pulse width measurement mode. Figure 12.8 shows an operation example in pulse width measure-

ment mode.

Item

Specification

Count source

f1, f2, f8, f32

Count operation

• Down-count

• Continuously counts the selected signal only when the 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 continued

Count start condition

Write “1” (count start) to TXS bit in TXMR register

Count stop condition

Write “0” (count stop) to TXS bit in TXMR register

Interrupt request

• When Timer X underflows [Timer X interruption]

generation timing

• Rising or falling of CNTR0 input (end of measurement period) [INT1 interrupt]

INT1/CNTR0 pin function

Measurement pulse input

CNTR0 pin function

Programmable I/O port

Read from timer

Count value can be read by reading TX register

Same applies to PREX register.

Write to timer

Value written to TX register is written to both reload register and counter.

Same applies to PREX register.

Select function

• INT1/CNTR0 polarity switching function

“H” or “L” level duration can be selected with R0EDG bit as the input pulse measurement

Table 12.5 Pulse Width Measurement Mode Specifications

Figure 12.7 TXMR Register in Pulse Width Measurement Mode

12.1 Timer (Timer X)

Timer X mode register

SymbolAddressAfter reset

TXMR008B16

0016

Bit name

Function

Bit symbol

b7 b6 b5 b4 b3 b2 b1 b0

b1 b0

TXMOD1

TXMOD0

Operation mode

select bit 0, 1

1 1 : Pulse width measurement mode

R0EDG

INT1/CNTR0 polarity

switching bit(1)

TXMOD2

TXS

TXOCNT

Timer X count

start flag

0 : Stops counting

1 : Starts counting

Set to "0" in pulse width measurement mode

TXEDG

TXUND

NOTES:

1. IThe IR bit in the INT1IC register may be set to “1” (interrupt requested) when the R0EDG bit is rewritten.

Refer to the paragraph 19.2.5 “Changing Interrupt Factor” in the Usage Notes Reference Book.

Set to "0" in pulse width measurement mode

[CNTR0]

0 : Measures “H” level width

1 : Measures “L” level width

[INT1]

0 : Rising edge

1 : Falling edge

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