M16CSLASH1N datasheet(92/238 Pages) RENESAS

92 / 238 page

Rev.1.00

Oct 20, 2004

page 80 of 222

M16C/1N Group

12. Timers

REJ09B0007-0100Z

Table 12.7 Specifications of pulse period measurement mode

Timer X mode register

TXMOD0

TXMOD1

Operation mode

select bit 0, 1

(Note 1)

0 0 : Pulse period measurement mode

1 : Pulse period measurement mode

R0EDG

CNTR0 polarity

switching bit

(Note 1)

TXS

Operation mode

select bit 2 (Note 1)

Timer X count

start flag (Note 3)

0 : Stops counting

1 : Starts counting

0 : No effectual edge

1 : Effectual edge found

0 : No under flow

1 : Under flow found

TXMOD2

TXOCNT

0 : In pulse period measurement mode, set to "0"

Symbol

TXMR

Address

008B16

When reset

0016

Function

Bit name

Bit symbol

b1 b0

0 : Measures a measurement pulse from one

rising edge to the next rising edge

(Interrupt at rising edge)

1 : Measures a measurement pulse from one

falling edge to the next falling edge

(Interrupt at falling edge)

P30/TXOUT

select bit

TXEDG

Effectual edge

reception flag (Note 2)

TXUND

Timer X under

flow flag (Note 2)

Note 1: This bit should rewrite with inhibiting the CNTR0 interrupt. When using the interrupt, the interrupt must be enabled

after clearing the CNTR0 interrupt request bit to "0" using a MOV instruction.

Note 2: These bits are set to "0" by writing a "0" in a program. (Writing a "1" has no effect.)

Nothing is assigned to the pod probe for M16C/1N group (M301N2T-PRB).

Note 3: Execute the MOV instruction when stopping the timer X while pulse period measurement mode.

Note 1: Avoid a shorter period pulse input than double prescaler X period. Longer pulse for H width and L width than the

prescaler X period should be input to the CNTR0 pin. If shorter pulse than the period is input to the CNTR0 pin,

the input may be disabled.

Item

Specification

Count source

f1, f8, f32, fC32

Count operation

• Down count

• After valid edge of measurement pulse is input, the timer X reloads contents in the

reload register and continues counting in underflow of the second prescaler X.

Count start condition

Count start flag is set (=1)

Count stop condition

Count start flag is reset (=0)

Interrupt request generation timing • When Timer X underflows [Timer X interruption]

• Rising (R0EDG=0) or falling (R0EDG=1) of CNTR0 input [CNTR0 interruption or timer X interrupt]

CNTR0 pin function

Measurement pulse input (Note 1)

TXOUT pin function

Programmable I/O port

Read from timer

When reading Timer X register, the count value of buffer for read purpose can be read

out. The buffer of read purpose retains the content of Timer X register upon an active

edge of measurement pulse, and starts to read the content of Timer X register by reading

Timer X.

Write to timer

When a value is written to Timer X register, it is written to both reload register and counter.

Same applies to Prescaler X register.

Select function

• CNTR0 polarity switching function

The measurement period of pulse input can be selected to be a period from one rising

edge to the next rising edge or from one falling edge to the next falling edge by software.

12.2.5 Pulse Period Measurement Mode

In this mode, the timer measures the pulse period of an external signal fed to CNTR0 pin.

Table 12.7 lists specifications of pulse period measurement mode. Figure 12.11 shows the Timer X

mode register in pulse period measurement mode. Figure 12.12 shows the operation example.

Figure 12.11 Timer X mode register in pulse period measurement mode

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