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HARDWARE
7540 Group User
’
s Manual
1-31
(4) Programmable wait one-shot generation mode
In the programmable wait one-shot generation mode, the one-shot
pulse by the setting value of timer Z secondary can be output from
TZ
OUT
pin by software or external trigger to INT
0
pin after the wait
by the setting value of the timer Z primary. 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 (b5) of the timer Y, Z waveform output control register
(PUM). When
“
0
”
is set to b5 of PUM, after the wait during the in-
terval of the TZP setting value,
“
H
”
pulse during the interval of the
TZS setting value is output. When
“
1
”
is set to b5 of PUM, 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 EXPZP and EXPZS of PUM to
“
1
”
. As a result, the
waveforms of more accurate resolution can be output.
In the programmable 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 be-
comes 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 ac-
cepted, 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 trig-
ger 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.)
Notes on the programmable wait one-shot generation mode are
described below;
I
Notes on programmable wait one-shot generation mode
Count set value
In the programmable wait one-shot generation mode, values of
TZS, EXPZP and EXPZS are valid by writing to TZP. Even when
changing TZP is not required, write the same value again.
Write timing to TZP
In the programmable wait one-shot generation mode, when the
setting value is changed while the waveform is output, set by soft-
ware in order not to execute the writing to TZP and the timing of
timer underflow during the secondary interval simultanesously.
Usage of waveform extension function
The waveform extension function by the timer Z waveform exten-
sion control bit can be used only when
“
00
16
”
is set to Prescaler Z.
When the value other than
“
00
16
”
is set to Prescaler Z, be sure to
set
“
0
”
to EXPZP and EXPZS. Also, when the timer Y underflow is
selected as the count source, the waveform extension function
cannot be used.
Timer Z write mode
When using this mode, be sure to set
“
1
”
to the timer Z write con-
trol bit to select
“
write to latch only
”
.
Timer Z can stop counting by setting
“
1
”
to the timer Z count stop
bit in any mode.
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.)
FUNCTIONAL DESCRIPTION