Event Counter Mode With Free-Run Type Selected - Renesas M16C Series User Manual

M30240 Group

2.2.2.5 Event Counter Mode with Free-run Type Selected

In event counter mode, select functions from those listed in Table 2.5 . An example using the indicated
options is described below. Figure 2.15 shows the operation timing, and Figure 2.16 shows the set-up
procedure.
Table 2.5: Timer A event counter mode and free-run type functions
Item
O
Count source
Note j = i - 1, but j = 4 when i = 0
Operation
(1) Setting the count start flag to "1" causes the counter to count the falling edges of the count source.
(2) Even if an underflow occurs, the content of the reload register is not reloaded, but the count con-
tinues. At this time, the Timer Ai interrupt request bit goes to "1".
(3) If switching from an up count to a down count or vice versa while a count is in progress, the switch
takes effect from the next effective edge of the count source.
(4) Even if an overflow occurs, the content of the reload register is not reloaded, but the count contin-
ues. At this time, the Timer Ai interrupt request bit goes to "1".
FFFF
16
n
0000
16
"1"
Count start flag
"0"
"1"
Up/down flag
"0"
Timer Ai interrupt
"1"
request bit
"0"
Figure 2.15: Event counter mode timing and free-run type operation
Rev.1.00 Sep 24, 2003 Page 155 of 360
Set-up
Input signal to TAi (counting
IN
falling edges)
Input signal to TAi (counting
IN
rising edges)
Timer overflow (TB2/TAj
overflow)
n = reload register content
(2) Underflow
(1) Start count
Set to "1" by software
Cleared to "0" when interrupt request is accepted, or cleared by software
Item
O
Pulse output function
Count operation type
O
O
Factor for switching
between up and down
(3) Switch count
Set to "1" by software
Timer A
Set-up
No pulses output
Pulses output
Reload type
Free-run type
Up/Down flag contents
Input signal to TAi
OUT
(4) Overflow
Time