Fujitsu FR81S User Manual
CHAPTER 19: BASE TIMER
5. Operation
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER
: BASE TIMER
FUJITSU SEMICONDUCTOR CONFIDENTIAL
51
Figure 5-5 and Figure 5-6 show the count start timing.
Figure 5-5 Count Start Timing (Software Trigger)
Figure 5-6 Count Start Timing (External Activation Trigger (TGIN Signal), Effective Edge =
Rising Edge)
Note:
The external activation trigger (TGIN signal) entry method varies depending on the I/O mode specified by the
I/O selection register (BTSEL01). See "5.2 I/O Allocation".
When the down counter underflows after attempting to count down further from the value of "0000H", the
value (cycle) set in the base timer x cycle setting register (BTxPCSR) is reloaded to the down counter, which
continues to count down. If an underflow occurs, theUDIR 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 is set to "1".
Figure 5-7 shows the operation in case of an underflow.
Figure 5-7 Operation in Case of an Underflow
0000
H
2T to 3T (external trigger)
Load
Count clock
Reload value
Counter value
External activation
-1
-1
trigger
XXXX H
CTEN bit
STRG bit
1 T
Load
Count clock
Reload value
Counter value
-1
-1
000
H
UDIR
Load
Count clock
Counter value
Underflow
Reload value
-
-1
0000
H
-
1
MB91520 Series
MN705-00010-1v0-E
684