7540 datasheet(130/366 Pages) RENESAS

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2-54

REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

APPLICATION

7540 Group

2.4 Timer X

Fig. 2.4.18 Setting method for event counter mode (1)

2.4.5 Event counter mode

(1) Operation description

The timer X counts signals input from the P14/CNTR0 pin.

Except for this, the operation in event counter mode is the same as in timer mode.

The active edge of CNTR0 pin input signal can be selected from rising or falling by the CNTR0 active

edge switch bit.

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) Event counter mode setting method

Figure 2.4.18 and Figure 2.4.19 show the setting method for event counter mode of timer X.

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]

Event counter mode

CNTR0 active edge switch

0: Count at rising edge

CNTR0 interrupt request occurs at falling edge

1: Count at falling edge

CNTR0 interrupt request occurs at rising edge

Timer X count stop

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

Do not use f(XIN) at RC oscillation.

Process 4: Set timer count source set register.

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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