SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
7542 Group
MITSUBISHI MICROCOMPUTERS
30
PRELIMINAR
Y
Notice:
This
is not
a final
specification.
Some
parametric
limits
are
subject
to change.
Fig. 29 Block diagram of timer A and timer B
Timer A (low-order) latch (8)
Timer A (low-order) (8)
Timer A (high-order) latch (8)
Timer A (high-order) (8)
Data bus
Timer A interrupt
request
Compare
Capture
Timer B (low-order) latch (8)
Timer B (low-order) (8)
Timer B (high-order) latch (8)
Timer B (high-order) (8)
Data bus
Timer B interrupt
request
Compare
Capture
1/2
1/16
1/32
1/64
1/128
1/256
Timer A count
stop bit
Timer A
count source
selection bits
Ring
oscillator
Timer A write
control bit
Timer B write
control bit
1/2
1/16
1/32
1/64
1/128
1/256
Timer B count
stop bit
Timer B count source
selection bits
Frequency
divider
Ring
oscillator
XIN
“00”
“01”
“11”
Clock division
ratio selection bits
“10”
Frequency
divider
Fig. 27 Structure of timer A, B mode register
Fig. 28 Timer count source set register
Timer A, B mode register
(TABM : address 001D16, initial value: 0016)
b7
b0
Timer A write control bit
0 : Write to latch and timer simultaneously
1 : Write to only latch
Timer A count stop bit
0 : Count start
1 : Count stop
Timer B write control bit
0 : Write to latch and timer simultaneously
1 : Write to only latch
Timer B count stop bit
0 : Count start
1 : Count stop
Not used (return “0” when read)
Compare 0, 1 modulation mode bit
0: Disabled
1: Enabled
Compare 2, 3 modulation mode bit
0: Disabled
1: Enabled
b7
b0
Timer X count source selection bits
b1 b0
0
0 : f(XIN)/16
0
1 : f(XIN)/2
1
0 : f(XIN) (Note 1)
1
1 : Not available
Timer A count source selection bits
b4 b3 b2
000 : f(XIN)/16
001 : f(XIN)/2
010 : f(XIN)/32
011 : f(XIN)/64
100 : f(XIN)/128
101 : f(XIN)/256
110 : Ring oscillator output (Note 2)
111 : Not available
Timer B count source selection bits
b7 b6 b5
000 : f(XIN)/16
001 : f(XIN)/2
010 : f(XIN)/32
011 : f(XIN)/64
100 : f(XIN)/128
101 : f(XIN)/256
110 : Timer A underflow
111 : Not available
Notes 1: f(XIN) can be used as timer X count source when using
a ceramic resonator or ring oscillator.
Do not use it at RC oscillation.
2: Ring oscillator can be used when the ring oscillator is enabled by bit 3 of CPUM.
Timer count source set register
(TCSS : address 002A16, initial value: 0016)