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CHAPTER 12 16-BIT RELOAD TIMER
12.6.1
Internal Clock Mode (reload mode)
Synchronized with the internal count clock, the 16-bit reload timer is used for counting
down of the 16-bit counter, generating an interrupt request to the CPU for a counter
underflow. It can also output a toggle waveform from the timer output pin.
■ Operation in Internal Clock Mode (reload mode)
When counting is enabled (TMCSRL0/TMCSRL1:CNTE = 1) and the timer is started by the software
trigger bit (TMCSRL0/TMCSRL1:TRG) or external trigger, the value of the reload register (TMRD0/
TMRD1) is loaded into the counter, and counting starts. If the count enable bit and software trigger bit are
set to "1" simultaneously, counting starts simultaneously with the enabling of counting.
When an underflow of the counter value (from 0000
register (TMRD0/TMRD1) is loaded into the counter, and counting continues. If the underflow interrupt
flag (TMCSRL0/TMCSRL1:UF) bit is set to "1" and the underflow interrupt enable (TMCSRL0/
TMCSRL1:INTE) bit is "1", an interrupt request is generated.
The timer can also output from the TO0/TO1 pin a toggle waveform, which is inverted for each underflow.
●
Software trigger operation
When "1" is written to the TRG bit of the timer control status register (TMCSRL0/TMCSRL1), the counter
is started. Figure 12.6-4 shows software trigger operation in reload mode.
Figure 12.6-4 Count Operation in Teload Mode (Software Trigger Operation)
Count clock
Data load signal
CNTE bit
T: Machine cycle
* It takes 1T time from trigger input to loading of the reload data.
246
Reload data
Counter
UF bit
TRG bit
TO pin
to FFFF
H
Reload data
Reload data
) occurs, the value of the 16-bit reload
H
Reload data
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