Fujitsu FR81S User Manual
CHAPTER 19: BASE TIMER
5. Operation
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER
: BASE TIMER
FUJITSU SEMICONDUCTOR CONFIDENTIAL
53
5.4.3. Operation in One-Shot Mode
This section explains the operation in one-shot mode.
This section explains the operation in one-shot mode.
Overview
In this mode, the counter will no longer count down once an underflow occurs.
To use this mode, set one-shot mode by setting the MDSE bit of the base timer x timer control register
(BTxTMCR) to "1"(MDSE=1).
Operation
Activation
The same operation as in reload mode. See "Overview" in "5.4.2 Operation in Reload Mode".
Counting Operation
The operation is the same as in reload mode until an underflow occurs. See "Overview". When the down
counter underflows, the value (cycle) set in the base timer x cycle setting register (BTxPCSR) is reloaded to
the down counter. However, the down counter stops counting. If an underflow occurs, the UDIR bit of the
base timer x status control register (BTxSTC) changes to "1". At this time, an underflow interrupt request
occurs if the UDIE bit of the base timer x status control register (BTxSTC) is set to "1".
Figure 5-9 shows the operation in case of an underflow.
Figure 5-9 Operation in Case of an Underflow
Output Waveform
The waveform (TOUT signal) of the 16/32-bit reload timer can be output. The waveform (TOUT signal) to be
output varies according to the setting of the OSEL bit of the base timer x timer control register (BTxTMCR).
Table 5-2 shows the correspondence between output polarities and output waveforms.
Table 5-2 Correspondence between Output Polarities and Output Waveforms
Output polarity
Output waveform
Normal polarity
(OSEL = 0)
When an activation trigger is input (counting in progress), "H" level pulse is output.
"L" level pulse is output while the timer waits for an activation trigger.
Inverted polarity
(OSEL = 1)
When an activation trigger is input (counting in progress), "L" level pulse is output.
"H" level pulse is output while the timer waits for an activation trigger.
0000
H
UDIR
Load
Count clock
Counter value
Underflow
Reload value
-1
-1
MB91520 Series
MN705-00010-1v0-E
686