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CHAPTER 11 16-BIT RELOAD TIMER
11.6.2 Internal Clock Mode (Single-shot Mode)
The 16-bit reload timer count downs the 16-bit down counter in synchronization with
the internal count clock and outputs an interrupt request when an underflow occurs
(change from "0000H" to "FFFFH"). It can also output a square waveform from the T0
pin.
s Internal Clock Mode (Single-Shot Mode)
When the software trigger bit (TRG) is set to "1" while the count enable bit (CNTE) of the timer
control status register (TMCSR) is set to "1" or a valid edge (rising, falling, or both edges) of
trigger input specified in the operation mode setting bits (MOD2, MOD1, and MOD0) is input to
the TIN pins, a value stored in the 16-bit reload register (TMRLR0/TMRHR0, TMRLR1/
TMRHR1) is loaded into the 16-bit down counter and countdown starts. When both the CNTE
bit and the software trigger bit (TMCSR: TRG) are set to "1", countdown starts as soon as
counting is enabled.
When an underflow of the 16-bit down counter occurs (change from "0000H" to "FFFFH"), the
16-bit down counter stops counting at the value "FFFFH".
An interrupt request is output when an underflow of the 16-bit down counter occurs while the
underflow interrupt request flag bit (UF) of the timer control status register (TMCSR) is set to "1"
and the underflow interrupt request enable bit (INTE) is set to "1".
The timer can also output from the TO pin a rectangular waveform indicating that counting is in
progress.
r Software trigger operation
Counting starts when the software trigger bit (TRG) is set to "1" while the count enable bit
(CNTE) of the timer control status register (TMCSR) is set to "1".
Figure 11.6-7 Count Operation in Single-Shot Mode (Software Trigger Operation)
Internal count clock
Counter
Data load signal
CNTE bit
UF bit
TRG bit
0000H
TO pin
T*
-1
FFFFH
0000H
-1
FFFFH
Wait for trigger input
T: Machine cycle
* It takes 1T time from trigger input to loading of the reload data.
Reload data