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7542 Group
b 7
b 0
T i m e r A , B m o d e r e g i s t e r
( T A B M : a d d r e s s 0 0 1 D
T i m e r A w r i t e c o n t r o l b i t
0 : W r i t e t o l a t c h a n d t i m e r s i m u l t a n e o u s l y
1 : W r i t e t o o n l y l a t c h
T i m e r A c o u n t s t o p b i t
0 : C o u n t s t a r t
1 : C o u n t s t o p
T i m e r B w r i t e c o n t r o l b i t
0 : W r i t e t o l a t c h a n d t i m e r s i m u l t a n e o u s l y
1 : W r i t e t o o n l y l a t c h
T i m e r B c o u n t s t o p b i t
0 : C o u n t s t a r t
1 : C o u n t s t o p
N o t u s e d ( r e t u r n " 0 " w h e n r e a d )
C o m p a r e 0 , 1 m o d u l a t i o n m o d e b i t
0 : D i s a b l e d
1 : E n a b l e d
C o m p a r e 2 , 3 m o d u l a t i o n m o d e b i t
0 : D i s a b l e d
1 : E n a b l e d
Fig. 29 Structure of timer A, B mode register
Frequency
Clock division
divider
ratio selection
"00"
1/2
bits
"01"
1/16
"11"
X
IN
1/32
On-chip
1/64
oscillator
"10"
1/128
CPU mode register
1/256
On-chip
oscillator
Frequency
divider
1/2
1/16
1/32
1/64
1/128
1/256
Timer B count source
Fig. 31 Block diagram of timer A and timer B
Rev.3.02
Oct 31, 2006
REJ03B0006-0302
, i n i t i a l v a l u e : 0 0
1 6
Timer A
Timer A count
count source
stop bit
selection bits
selection bits
Timer B count
stop bit
Page 34 of 134
b7
)
1 6
Notes 1: f(X
) can be used as timer X count source when using
IN
a ceramic resonator or on-chip oscillator.
Do not use it at RC oscillation.
2: On-chip oscillator can be used when the on-chip oscillator
is enabled by bit 3 of CPUM.
Fig. 30 Timer count source set register
Data bus
Timer A (low-order) latch (8)
Timer A (low-order) (8)
Data bus
Timer B (low-order) latch (8)
Timer B (low-order) (8)
b0
Timer count source set register
(TCSS : address 002A
, initial value: 00
16
Timer X count source selection bits
b1 b0
0
0 : f(X
)/16
IN
0
1 : f(X
)/2
IN
1
0 : f(X
) (Note 1)
IN
1
1 : Not available
Timer A count source selection bits
b4 b3 b2
0
0
0 : f(X
)/16
IN
0
0
1 : f(X
)/2
IN
0
1
0 : f(X
)/32
IN
0
1
1 : f(X
)/64
IN
1
0
0 : f(X
)/128
IN
1
0
1 : f(X
)/256
IN
1
1
0 : On-chip oscillator output (Note 2)
1
1
1 : Not available
Timer B count source selection bits
b7 b6 b5
0
0
0 : f(X
)/16
IN
0
0
1 : f(X
)/2
IN
0
1
0 : f(X
)/32
IN
0
1
1 : f(X
)/64
IN
1
0
0 : f(X
)/128
IN
1
0
1 : f(X
)/256
IN
1
1
0 : Timer A underflow
1
1
1 : Not available
Timer A (high-order) latch (8)
Timer A (high-order) (8)
Timer B (high-order) latch (8)
Timer B (high-order) (8)
)
16
Timer A write
control bit
Timer A interrupt
request
Compare
Capture
Timer B write
control bit
Timer B interrupt
request
Compare
Capture
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