
Under
Specifications in this manual are tentative and subject to change
Rev. G
Timer B
1-89
MITSUBISHI MICROCOMPUTERS
M30222 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Fig. 1.65. Timer Bi mode register in event counter mode
Table 1.31. Timer specifications in event counter mode
Item
Specification
Count source
External signals input to TBiIN pin
Effective edge of count source can be a rising edge or falling edge or both as
selected by software
Count operation
Count down
When the timer underflows, it reloads the reload register content before conti-
nous counting.
Divide ratio
1/(n + 1) n: Set value
Count start condition
Count start flag is set (=i)
Count stop condition
Count start flag is reset (=0)
Interrupt request
generation timing
The timer underflows.
TBiIN pin function
Count source input
Read from timer
Count value can be read out by reading Timer Bi register
Write to timer
When counting stops
When a value is written to Timer Bi register, it is written to both reload register
and counter.
When counting is in progress
When a value is written to Timer Bi register, it is written to only reload register.
(Transferred to counter at next reload time).
Timer Bi mode register
Symbol
TBiMR(i=0 to 5)
Address
When reset
00XX0000
2
00XX0000
2
039B
16
to 039D
16
035B
16
to 035D
16
Bit name
Function
Bit symbol
TMOD0
W
R
b7
b6
b5
b4
b3
b2
b1
0
b0
1
Operation mode select bit
0 1 : Event counter mode
b1 b0
TMOD1
MR0
Count polarity select
bit
(Note 1)
MR2
MR1
MR3
Invalid in event counter mode.
In an attempt to write to this bit, write
“
0
”
. If read, the value in
event counter mode, is indeterminate.
TCK1
TCK0
0 0 : Counts external signal's
falling edges
0 1 : Counts external signal's
rising edges
1 0 : Counts external signal's
falling and rising edges
1 1 : Inhibited
b3 b2
Nothing is assigned (i = 1, 2, 4, 5).
Write "0" when writing to this bit. If read, the value
is indeterminate.
Note 1: Valid only when input from the TBi
IN
pin is selected as the event clock.
If timer's overflow is selected, this bit can be
“
0
”
or
“
1
”
.
Note 2: Timer B0, Timer B3.
Note 3: Timer B1, Timer B2, Timer B4, Timer B5.
Note 4: Set the corresponding port direction register to
“
0
”
.
Invalid in event counter mode.
Can be
“
0
”
or
“
1
”
.
Event clock select
0 : Input from TBi
IN
pin (Note 4)
1 : TBj overflow
(j = i
–
1; however, j = 2 when i = 0,
j = 5 when i = 3)
0 (Fixed to
“
0
”
in event counter mode; i = 0, 3)
(Note 2)
(Note 3)