Long-Period Timers - Renesas M16C Series User Manual

M30245 Group

3.1 Long-Period Timers

Overview
Specifications
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Operation
Timer A0 count
start flag
Timer A1 count
start flag
Timer A0 interrupt
request bit
Timer A1 interrupt
request bit
Figure 3.1.1. Operation timing of long-period timers
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
In this process, Timer A0 and Timer A1 are connected to make a 16-bit timer with a 16-bit
prescaler. Figure 3.1.1 shows the operation timing, Figure 3.1.2 shows the connection dia-
gram, and Figures 3.1.3 and 3.1.4 show the set-up procedure.
Use the following peripheral functions:
• Timer mode of timer A
• Event counter mode of timer A
(1) Set timer A0 to timer mode, and set timer A1 to event counter mode.
(2) Perform a count on count source f
on timer A0 using timer A1 to count for 1 second.
(3) Connect a 16-MHz oscillator to X
(1) Setting the count start flag to "1" causes the counter to begin counting. The counter of
timer A0 performs a down count on count source f
(2) If the counter of timer A0 underflows, the counter reloads the content of the reload register
and continues counting. At this time, the timer A0 interrupt request bit goes to "1". The
counter of timer A1 performs a down count on underflows in timer A0.
(3) If the counter of timer A1 underflows, the counter reloads the content of the reload register
and continues counting. At this time, the timer A1 interrupt request bit goes to "1".
l = reload register content
FFFF (1) Start count (2) Timer A0 underflow
16
l
0000
16
n = reload register content
FFFF
Start count.
16
n
0000
16
Set to "1" by software
"1"
"0"
"1"
"0"
"1"
"0"
"1"
"0"
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using timer A0 to count for 1 ms, and perform a count
1
.
IN
.
1
Cleard "0" by software
Cleared to "0" when interrupt request is accepted, or cleared by software
3. Timer A Applications
(3) Timer A1 underflow
Set to "1" by software
Time
Time