7540 datasheet(106/366 Pages) RENESAS

106 / 366 page

2-30

REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

APPLICATION

7540 Group

2.2 Timer A

Fig. 2.2.21 Setting method for pulse width HL continuously measurement mode (1)

2.2.6 Pulse width HL continuously measurement mode

(1) Operation description

In the pulse width HL continuously measurement mode, the pulse width (“H” and “L” levels) input to

the P00/CNTR1 pin is measured.

CNTR1 interrupt request is generated at both rising and falling edges of CNTR1 pin input signal.

Except for this, the operation in pulse width HL continuously measurement mode is the same as in

period measurement mode.

The count value when trigger input from the CNTR1 pin is accepted is retained until Timer A is read once.

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

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

(2) Pulse width HL continuously measurement mode setting method

Figure 2.2.21 and Figure 2.2.22 show the setting method for pulse width HL continuously measurement

mode of timer A.

b7b0

11 1

b7b0

Process 1: Disable timer A interrupt and CNTR1 interrupt.

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

CNTR1 interrupt disabled

Port P0 direction register (P0D) [Address 0116]

Set the P00/CNTR1 pin to the input mode

Process 2: Set the CNTR1 pin to the input mode.

Interrupt control register 2 (ICON2) [Address 3F16]

Timer A interrupt disabled

Process 3: Set the pull-up control register.

Pull-up control register (PULL) [Address 1616]

P00/CNTR1 pull-up control bit

0: Pull-up Off

1: Pull-up On

Process 4: Set timer A mode register.

Timer A mode register (TAM) [Address 1D16]

Pulse width HL continuously measurement mode

Timer A count stop

Process 5: Set the count value to timer A (Note).

• Set the initial value to timer A (low-order)

Timer A (low-order) (TAL) (Address 1E16)

Initial value

Timer A (high-order) (TAH) (Address 1F16)

Note: Write both registers in order of timer X (low-order) and the timer X (high-order) following, certainly.

Initial value

• Set the initial value to timer A (high-order)

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