7480 datasheet(22/98 Pages) RENESAS

22 / 98 page

MITSUBISHI MICROCOMPUTERS

7480/7481 GROUP

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

PRELIMINAR

Notice:

This

is not

a final

specification.

Some

parametric

limits

are

subject

to change.

the timer value provided before the start of measurement.

Figure 21 shows a timing diagram in the pulse cycle measurement

mode.

(4) Pulse Width Measurement Mode

q Mode Selection

This mode is selected by setting b2, b1 and b0 of TXM or TYM

to “011”.

q Count Source Selection

The count source is f(XIN)/2, f(XIN)/8 or f(XIN)/16.

q Interrupt

The underflow interrupt is the same as the timer event count

mode. Set b2 or b3 of IREQ2 to “1” as soon as pulse width

measurement is completed.

q Explanation of Operation

While a timer operation stops

Select a timer count source. Next, select a pulse width to be

measured. A timer counts a period from a falling edge to a rising

edge of the CNTR0/CNTR1 pin input (“L” period) when b2 or b3

of EG is “1”. A timer counts a period from a rising edge to a fall-

ing edge of the CNTR0/CNTR1 pin input (“H” period) when b2 or

b3 of EG is set to “0”.

While a timer operation is enabled

At setting b0 and b1 of TXYCON to “0”, a timer starts to mea-

sure a pulse width, and starts to count down from the count

value provided before measurement. When the active edge is

detected at measurement completion, 1’s complement of the

timer value is set in the timer latch. When the active edge is de-

tected at measurement completion or measurement start,

“FFFF16” is set in the timer. When a timer underflows, a timer X

or timer Y interrupt occurs, and “FFFF16” is set in the timer.

A measurement value is held until the next measurement is

completed. In this mode, set the port in common with the

CNTR0/CNTR1 pin as an input port.

q Interrupt

The timer underflow interrupt is the same as the timer event

count mode.

q Explanation of Operation

This operation is the same as the timer event count mode ex-

cept that a timer outputs a pulse from the CNTR0/CNTR1 pin in

which the polarity of output level is inverted at each timer

underflow. When the CNTR0 edge selection bit (b2) or CNTR1

edge selection bit (b3) of EG is “0”, the output of the CNTR0/

CNTR1 pin is started with an “H” level output. When b2 or b3 of

EG is “1”, the output of this pin is started with an “L” level. In this

mode, set the port in common with the CNTR0/CNTR1 pin as an

output port.

s Note

While a timer operation stops

The output level of the CNTR0/CNTR1 pin is initialized to the value

set in the CNTR0 edge selection bit or CNTR1 edge selection bit

by writing to the timer.

While a timer operation is enabled

The output level of the CNTR0/CNTR1 pin is inverted by changing

the CNTR0 edge selection bit or CNTR1 edge selection bit.

Figure 20 shows a timing diagram in the pulse output mode.

(3) Pulse Cycle Measurement Mode

q Mode Selection

This mode is selected by setting b2, b1 and b0 of TXM or TYM

to “010”.

q Count Source Selection

The count source is f(XIN)/2, f(XIN)/8 or f(XIN)/16.

q Interrupt

The underflow interrupt is the same as the timer event count

mode. Set b2 or b3 of IREQ2 to “1” as soon as the pulse cycle

measurement is completed.

q Explanation of Operation

While a timer operation stops

Select a timer count source. Next, select a pulse cycle to be

measured. When b2 or b3 of EG is “0”, a timer counts a period

from a falling edge to a falling edge of the CNTR0/CNTR1 pin in-

put.

When b2 or b3 of EG is “1”, a timer counts a period from a ris-

ing edge to a rising edge of the CNRT0/CNTR1 pin input.

While a timer operation is enabled

At setting b0 and b1 of TXYCON to “0”, a timer starts to mea-

sure the pulse cycle, and starts to count down from the count

value provided before measurement. When an active edge is

detected at measurement completion or measurement start, 1's

complement of the timer value is set to the timer latch and

“FFFF16” is set in the timer.

When a timer underflows, a timer X or timer Y interrupt occurs,

and “FFFF16” is set in the timer. A measurement value is held

until the next measurement is completed. In this mode, set the

port in common with the CNTR0/CNTR1 pin as an input port.

s Note

The timer value cannot be read in this mode. A timer value can be

set while a timer operation stops (no measurement).

Since the timer latch of this mode becomes read only, do not per-

form a write operation during measurement.

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

active edge of pulse cycle measurement is detected.

Accordingly, the timer value at a start of measurement depends on

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