7540 datasheet(134/366 Pages) RENESAS

134 / 366 page

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REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

APPLICATION

7540 Group

2.4 Timer X

2.4.6 Pulse width measurement mode

(1) Operation description

In the pulse width measurement mode, the pulse width of the signal input to P14/CNTR0 pin is

measured.

The operation of Timer X can be controlled by the level of the signal input from the CNTR0 pin.

When the CNTR0 active edge switch bit is “0”, the signal selected by the timer X count source

selection bit is counted while the input signal level of CNTR0 pin is “H”. The count is stopped while

the pin is “L”. Also,

when the CNTR0 active edge switch bit is “1”, the signal selected by the timer X count source

selection bit is counted while the input signal level of CNTR0 pin is “L”. The count is stopped while

the pin is “H”.

Timer X can stop counting by setting “1” to the timer X count stop bit.

Also, when Timer X underflows, the timer X interrupt request bit is set to “1”.

(2) Pulse width HL continuously measurement mode setting method

Figure 2.4.23 and Figure 2.4.24 show the setting method for pulse width measurement mode of timer X.

Fig. 2.4.23 Setting method for pulse width measurement mode (1)

b7b0

Process 1: Disable timer X interrupt and CNTR0 interrupt.

Interrupt control register 1 (ICON1) [Address 3E16]

CNTR0 interrupt disabled

Timer X interrupt disabled

Port P1 direction register (P1D) [Address 0316]

Set the P14/CNTR0 pin to the input mode

Process 2: Set the CNTR0 pin to the input mode.

Process 3: Set timer X mode register.

Timer X mode register (TXM) [Address 2B16]

Pulse width measurement mode

CNTR0 active edge switch

0: “H” level width measurement

1: “L” level width measurement

Timer X count stop

Note: f(XIN) can be used only when a ceramic resonator or an on-chip oscillator is used.

Do not use f(XIN) at RC oscillation.

Process 4: Set timer X count source.

Timer count source set register (TCSS) [Address 2E16]

Timer X count source selection bits

b1 b0

0 0 : f(XIN)/16

0 1 : f(XIN)/2

1 0 : f(XIN) (Note)

1 1 : Not available

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