Fujitsu FR81S Manual Do Utilizador
CHAPTER 21: 32-BIT FREE-RUN TIMER
5. Operation
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER
: 32-BIT FREE-RUN TIMER
FUJITSU SEMICONDUCTOR CONFIDENTIAL
27
5.1.1. Count Operation
This section shows the count operation.
The free-run timer will be incremented based on the input clock (internal clock or external clock). If the
external clock mode (TCCSH.ECKE = 1) is selected, the free-run timer starts counting up by the rising and
falling edges of the external input clock.
The first rising and falling edges of the external clock immediately after the selection of external clock mode
will be ignored. This means that the first falling edge will be ignored if the initial value of the external clock
input is "1", and the first rising edge will be ignored if the initial value is "0".
(1) Reset
(2) Clearing of the free-run timer by reset (Count value "0000_0000
H
")
(3) Count up operation by the free-run timer
(4) Compare clear match of the free-run timer and interrupt generation
(5) Clearing of the free-run timer by compare clear match (Count value "0000_0000
H
")
(6) Repetition of step (3) to (5)
(7) The free-run timer counts up in the clock obtained by dividing the internal clock (count clock).
(8) The free-run timer counts up in the count clock obtained by synchronizing the external clock with the internal
clock.
Count
timing
Count of free-
run timer
Reset
Compare clear match
interrupt request
Clearing
free-run timer
Count of
free-run
timer
Time
FFFF
Internal clock
(F
CLKP
/2)
External pin
(CKI)
Count of free-
run timer
Clearing by software
Clearing by software
(Internal clock)
(1)
(5)
(2)
Count
timing
P
e
r
iphe
r
al
clo
c
k (CLKP)
00000000
H
(2)
(3)
(4)
(8)
(5)
(7)
( External clock
F
CLKP
/2 )
CPCLR
External clock input
Count clock
Count
value
N
TCCSH
:
ECKE
The first edge immediately after
external
clock
selection is ignored
φ
N+1
MB91520 Series
MN705-00010-1v0-E
822