TIMER A
7.3 Timer mode
7.3.3 Select function
In timer Aj (j = 0 to 2, 4, 9), the gate function or pulse output function can be selected.
The following describes the gate and pulse output functions.
(1) Gate function
The gate function is selected by setting the gate function select bits (bits 4 and 3 at addresses 5616
to 5816, 5A16, DA16) to “10
2
” or “11 .” The gate function makes it possible to start or stop counting
2
depending on the TAjIN pin’s input signal. Table 7.3.2 lists the count valid levels.
Figure 7.3.4 shows an example of operation with the gate function selected.
When selecting the gate function, set the port P2 and port P6 direction registers’ bits which correspond
to the TAjIN pins for the input mode. Additionally, make sure that the TAjIN pin’s input signal has a
pulse width equal to or more than two cycles of the count source.
Table 7.3.2 Count valid levels
Gate function select bits
Count valid level (Duration while counter counts)
b4
1
b3
0
While TAjIN pin’s input signal level is at “L” level
While TAjIN pin’s input signal level is at “H” level
1
1
Note: The counter does not count while the TAjIN pin’s input signal is not at the count valid level.
FFFF16
n
➀ Starts counting.
➀ Stops counting.
000016
Time
Set to “1” by software.
Count start bit
Count valid
level
Invalid level
TAjIN pin’s
input signal
Timer Aj interrupt
request bit
➀ The counter counts while the count start bit = “1” and the TAjIN pin’s input signal is at the count valid level.
➀ The counter stops counting while the TAjIN pin’s input signal is not at the count valid level, and the counter
value is retained.
Cleared to “0” when
interrupt request is
accepted or cleared
by software.
n : Reload register’s contents
Fig. 7.3.4 Example of operation with gate function selected
7906 Group User’s Manual Rev.2.0
7-15
RENESAS [ RENESAS TECHNOLOGY CORP ]
