M38040FFHKP datasheet(32/116 Pages) RENESAS

32 / 116 page

Rev.1.01

Jan 25, 2005

page 32 of 114

REJ03B0131-0101Z

3804 Group (Spec. H)

(4) Pulse period measurement mode

qMode selection

This mode can be selected by setting “010” to the timer Z operat-

ing mode bits (bits 2 to 0) and setting “0” to the timer/event

counter mode switch bit (b7) of the timer Z mode register (address

002A16).

qCount source selection

In high- or middle-speed mode, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64,

1/128, 1/256, 1/512 or 1/1024 of f(XIN); or f(XCIN) can be selected

as the count source.

In low-speed mode, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256,

1/512 or 1/1024 of f(XCIN); or f(XCIN) can be selected as the count

source.

qInterrupt

The interrupt at an underflow is the same as the timer mode’s.

When the pulse period measurement is completed, the INT4/

CNTR2 interrupt request bit (bit 5) of the interrupt request register

2 (address 003D16) is set to “1”.

qExplanation of operation

The cycle of the pulse which is input from the CNTR2 pin is mea-

sured. When the CNTR2 active edge switch bit (bit 5) of the timer

Z mode register (address 002A16) is “0”, the timer counts during

the term from one falling edge of CNTR2 pin input to the next fall-

ing edge. When it is “1”, the timer counts during the term from one

rising edge input to the next rising edge input.

When the valid edge of measurement completion/start is detected,

the 1’s complement of the timer value is written to the timer latch

and “FFFF16” is set to the timer.

Furthermore when the timer underflows, the timer Z interrupt re-

quest occurs and “FFFF16” is set to the timer. When reading the

timer Z, the value of the timer latch (measured value) is read. The

measured value is retained until the next measurement comple-

tion.

sPrecautions

Set the double-function port of CNTR2 pin and port P47 to input in

this mode.

A read-out of timer value is impossible in this mode. The timer can

be written to only during timer stop (no measurement of pulse pe-

riod).

Since the timer latch in this mode is specialized for the read-out of

measured values, do not perform any write operation during mea-

surement.

“FFFF16” is set to the timer when the timer underflows or when the

valid edge of measurement start/completion is detected. Conse-

quently, the timer value at start of pulse period measurement

depends on the timer value just before measurement start.

Figure 28 shows the timing chart of the pulse period measurement

mode.

(5) Pulse width measurement mode

qMode selection

This mode can be selected by setting “011” to the timer Z operat-

ing mode bits (bits 2 to 0) and setting “0” to the timer/event

counter mode switch bit (b7) of the timer Z mode register (address

002A16).

qCount source selection

In high- or middle-speed mode, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64,

1/128, 1/256, 1/512 or 1/1024 of f(XIN); or f(XCIN) can be selected

as the count source.

In low-speed mode, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256,

1/512 or 1/1024 of f(XCIN); or f(XCIN) can be selected as the count

source.

qInterrupt

The interrupt at an underflow is the same as the timer mode’s.

When the pulse widths measurement is completed, the INT4/

CNTR2 interrupt request bit (bit 5) of the interrupt request register

2 (address 003D16) is set to “1”.

qExplanation of operation

The pulse width which is input from the CNTR2 pin is measured.

When the CNTR2 active edge switch bit (bit 5) of the timer Z mode

from one rising edge input to the next falling edge input (“H” term).

When it is “1”, the timer counts during the term from one falling

edge of CNTR2 pin input to the next rising edge of input (“L” term).

When the valid edge of measurement completion is detected, the

1’s complement of the timer value is written to the timer latch.

When the valid edge of measurement completion/start is detected,

“FFFF16” is set to the timer.

When the timer Z underflows, the timer Z interrupt occurs and

“FFFF16” is set to the timer Z. When reading the timer Z, the value

of the timer latch (measured value) is read. The measured value is

retained until the next measurement completion.

sPrecautions

Set the double-function port of CNTR2 pin and port P47 to input in

this mode.

A read-out of timer value is impossible in this mode. The timer can

be written to only during timer stop (no measurement of pulse

widths).

Since the timer latch in this mode is specialized for the read-out of

measured values, do not perform any write operation during mea-

surement.

“FFFF16” is set to the timer when the timer underflows or when the

valid edge of measurement start/completion is detected. Conse-

quently, the timer value at start of pulse width measurement

depends on the timer value just before measurement start.

Figure 29 shows the timing chart of the pulse width measurement

mode.

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