7540 Group User
’
s Manual
APPLICATION
2-91
2.5 Timer Y and timer Z
2.5.6 Programmable wait one-shot generation mode (timer Z)
(1) Operation description
In the programmable wait one-shot generation mode, the one-shot pulse by the setting value of timer
Z secondary (TZS) can be output from P0
2
/TZ
OUT
pin by software or external trigger to P3
7
/INT
0
pin
after the wait by the setting value of the timer Z primary (TZP). When using this mode, be sure to
set
“
1
”
to the timer Z write control bit to select
“
write to latch only
”
. Also, set the port P0
2
direction
registers to output mode.
The active edge of output waveform is set by the timer Z output level latch. When
“
0
”
is set to the
timer Z output level latch, after the wait during the interval of the TZP setting value,
“
H
”
pulse during
the interval of the TZS setting value is output. When
“
1
”
is set to the timer Z output level latch, after
the wait during the interval of the TZP setting value,
“
L
”
pulse during the interval of the TZS setting
value is output.
Also, in this mode, the intervals of the wait and the one-shot pulse output can be extended for 0.5
cycle of timer count source clock by setting the timer Z primary waveform extension control bit
(EXPZP) and the timer Z secondary waveform extension control bit (EXPZS) to
“
1
”
. As a result, the
waveforms of more accurate resolution can be output.
In the programmable wait one-shot generation mode, the trigger by software or the external INT
0
pin
can be accepted by writing
“
0
”
to the timer Z count stop bit after the count value is set. (At the time
when
“
0
”
is written to the timer Z count stop bit, Timer Z stops.)
By writing
“
1
”
to the timer Z one-shot start bit, or by inputting the valid trigger to the INT
0
pin after
the trigger to the INT
0
pin becomes valid by writing
“
1
”
to the INT
0
pin one-shot trigger control bit,
Timer Z starts counting.
While Timer Z counts the TZP, the initial value of the TZ
OUT
pin output is retained. When Timer Z
underflows, the value of TZS is reloaded, at the same time, the output of TZ
OUT
pin is inverted.
When Timer Z underflows, the output of TZ
OUT
pin is inverted again and Timer Z stops. When also
the trigger of INT
0
pin is accepted, the contents of the one-shot start bit is changed to
“
1
”
by
hardware.
The falling or rising can be selected as the edge of the valid trigger of INT
0
pin by the INT
0
pin one-
shot trigger edge selection bit.
During the wait interval and the one-shot pulse output interval, the one-shot pulse output can be
stopped forcibly by writing
“
0
”
to the timer Z one-shot start bit.
In the programmable wait one-shot generation mode, when the count values are changed, set values
to the TZS, EXPZP and EXPZS first. After then, set the value to TZP. The values are set all at once
at the beginning of the next wait interval when the value is set to TZP. (When writing at timer stop
is executed, writing to TZP at last is required.)
Timer Z can stop counting by setting
“
1
”
to the timer Z count stop bit.
Also, when timer Z underflows, the timer Z interrupt request bit is set to
“
1
”
.
Timer Z reloads the value of latch when counting is stopped by the timer Z count stop bit.
(When timer is read out while timer is stopped, the value of latch is read. The value of timer can be
read out only while timer is operating.)