Renesas 7700 FAMILY, User Manual

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TIMER A
7751 Group User’s Manual 5–35
5.5 One-shot pulse mode
5.5.3 Trigger
The counter is enabled for counting when the count start bit (address 40
16
) is set to “1.” The counter starts
counting when a trigger is generated after it has been enabled. An internal or an external trigger can be
selected as that trigger.
An internal trigger is selected when the trigger select bits (bits 4 and 3 at addresses 56
16
to 5A
16
) are “00
2
”
or “01
2
”; an external trigger is selected when the bits are “10
2
” or “11
2
.”
If a trigger is generated during counting, the reload register’s contents are reloaded and the counter
continues counting. If generating a trigger during counting, make sure that a certain time which is equivalent
to one cycle of the timer’s count source or more has passed between the previous generated trigger and
a new generated trigger.
(1) When selecting internal trigger
A trigger is generated when writing “1” to the one-shot start bit (address 42
16
). Figure 5.5.4 shows
the structure of the one-shot start register.
(2) When selecting external trigger
A trigger is generated at the falling of the TAi
IN
pin’s input signal when bit 3 at addresses 56
16
to 5A
16
is “0,” or at its rising when bit 3 is “1.”
When using an external trigger, set the port P5 and P6 direction registers’ bits which correspond to
the TAi
IN
pins for the input mode.
Fig. 5.5.4 Structure of one-shot start register
.
Bit
7 to 5 Nothing is assigned.
Timer A4 one-shot start bit
Timer A3 one-shot start bit
Timer A2 one-shot start bit
Timer A1 one-shot start bit
Timer A0 one-shot start bit
Bit name
At reset
0
0
Undefined
0
0
0
RW Functions
b7 b6 b5 b4 b3 b2 b1 b0
One-shot start register (Address 42
16
)
1 : Start outputting one-shot pulse
(valid when selecting internal
trigger.)
The value is “0” at reading.
0
1
2
3
4
WO
WO
WO
WO
WO
–