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CHAPTER 11 16-BIT RELOAD TIMER
MB90560 series
11.6
11.6.2 Single-shot Mode (Internal Clock Mode)
Operation of the 16-Bit Reload Timer
Synchronized with the internal count clock, the 16-bit reload timer is used for counting
down of the 16-bit counter and generating an interrupt request to the CPU when the
counter is underflow. It can also output to the TO pin a rectangular waveform indicating
that counting is in progress.
I
Single-shot mode (Internal clock mode)
When counting is enabled (TMCSR: CNTE = 1) and the timer is started with the software trigger
bit (TMCSR: TRG) or external trigger, 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
H
” to “FFFF
H
”) occurs, the counter stops in
the “FFFF
H
” state. If the underflow interrupt request flag (UF) bit is set to “1” and the interrupt
request enable (INTE) bit is “1”, an interrupt request is generated.
The timer can also output to the TO pin a rectangular waveform indicating that counting is in
progress.
G
Software trigger operation
When “1” is written to the TRG bit of the timer control status register (TMCSR), the counter is
started. Figure 11.6-7 shows the software trigger operation in single-shot mode.
Figure 11.6-7 Count operation in single-shot mode (software trigger operation)
Count clock
Counter
Data load signal
UF bit
CNTE bit
TRG bit
TO pin
Wait for trigger input
Reload data
Reload data
T: Machine cycle
* It takes 1T time from trigger input to loading of the reload data.