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7641

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

Mitsumi 

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MITSUBISHI MICROCOMPUTERS

7641 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

Timer X

Timer X is a 16-bit timer that can be selected in one of four modes.

The timer X’s internal clock and count source can be selected and

a write control is possible by using the timer X mode register.

In all modes the count operation can halt by setting the Timer X

Count Stop Bit to “1”. Additionally, each timer underflow sets the

Interrupt Request Bit to “1”.

(1) Timer Mode

The timer counts the SCSGCLK (Special Count Source Genera-

tor) or one of the internal clock φ divided by 8, 16, 32, 64.

(2) Pulse Output Mode

Each time the timer underflows, a signal output from the CNTR0

pin is inverted. Except for this, the operation in pulse output mode

is the same as in timer mode.

When the CNTR0 Active Edge Switch Bit is “0”, the CNTR0 pin

starts pulses output beginning at “H”; when this bit is “1”, the

CNTR0 pin starts pulses output beginning at “L”.

When using a timer in this mode, set the port P43 direction regis-

ter to output mode.

(3) Event Counter Mode

The timer counts signals input through the CNTR0 pin.

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

as in timer mode.

When the CNTR0 Active Edge Switch Bit is “0”, the rising edge is

counted; when this bit is “1”, the falling edge is counted.

When using a timer in this mode, set the port P43 direction regis-

ter to input mode.

(4) Pulse Width Measurement Mode

When the CNTR0 Active Edge Switch Bit is “0”, the timer counts

while the input signal of CNTR0 pin is at “H”; when it is “1”, the

timer counts while the input signal of CNTR0 pin is at “L”.

The timer counts the SCSGCLK or one of the internal clock φ di-

vided by 8, 16, 32, 64 as its count source.

When using a timer in this mode, set the port P43 direction regis-

ter to input mode.

s Notes

q Timer X Write Control

If the Timer X Write Control Bit is “1”, when the value is written in

the address of timer X, the value is loaded only in the latch. The

value in the latch is loaded in timer X after timer X underflows.

If the Timer X Write Control Bit is “0”, when the value is written in

the address of timer X, the value is loaded in the timer X and the

latch at the same time.

When the value is to be written in latch only, unexpected value

may be set in the high-order timer if the writing in high-order latch

and the underflow of timer X are performed at the same timing.

q CNTR0 Interrupt Active Edge Selection

The CNTR0 interrupt active edge depends on the selection of

CNTR0 Active Edge Switch Bit.

b7

b0

Timer X mode register (address 002716)

TXM

Timer X write control bit

0: Write value in latch and counter

1: Write value in latch only

Timer X count source select bits

b2b1

0 0: φ / 8

0 1: φ / 16

1 0: φ / 32

1 1: φ / 64

Timer X internal clock select bit

0: φ / n (n = 8, 16, 32, 64)

1: SCSGCLK (Special Count Source Generator)

Timer X operating mode bits

b5b4

0 0: Timer mode

0 1: Pulse output mode

1 0: Event counter mode

1 1: Pulse width measurement mode

CNTR0 active edge switch bit

0: Count at rising edge in event counter mode

Start from “H” output in pulse output mode

Measure “H” pulse width in pulse width

measurement mode

Falling edge active for interrupt

1: Count at falling edge in event counter mode

Start from “L” output in pulse output mode

Measure “L” pulse width in pulse width

measurement mode

Rising edge active for interrupt

Timer X count stop bit

0: Count start

1: Count stop

Fig. 20 Structure of timer X mode register

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