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Mitsubishi microcomputers
M16C / 62A Group (80-pin)
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Timer B
83
Item
Specification
Count source
External signals input to TBi
IN
pin
Effective edge of count source can be a rising edge, a falling edge, or falling
and rising edges as selected by software
Counts down
When the timer underflows, it reloads the reload register contents before
continuing counting
1/(n+1)
n : Set value
Count start flag is set (= 1)
Count start flag is reset (= 0)
Interrupt request generation timing
The timer underflows
TBi
IN
pin function
Count source input
Read from timer
Count value can be read out by reading timer Bi register
Write to timer
When counting stopped
When a value is written to timer Bi register, it is written to both reload register and counter
When counting 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)
Note: Timer B1 works exclusively as an internal timer since timer B1 does not have input port (TB1
IN
).
Count operation
Divide ratio
Count start condition
Count stop condition
(2) Event counter mode
In this mode, the timer counts an external signal or an internal timer's overflow. (See Table 1.13.7.)
Figure 1.13.18 shows the timer Bi mode register in event counter mode.
Table 1.13.7. Timer specifications in event counter mode
Figure 1.13.18. Timer Bi mode register in event counter mode
Timer Bi mode register
AA
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
b7
b6
b5
b4
b3
b2
b1
0 1
b0
AA
Operation mode select bit
0 1 : Event counter mode
b1 b0
TMOD1
MR0
Count polarity select
bit
(Note 1)
MR2
MR1
MR3
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
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”. Since Timer B1 does
not have TB1
IN
pin, the setting value of this bit is invaid.
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”. Since Timer B1 does not
have TB1
IN
pin, do not use TB1
IN
pin as event clock.
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)
AA
(Note 3)
AAA
AAA
AAA
AA
AA
AA
A
A
A
A
AAA
AAA
AA
Invalid in event counter mode.
In an attempt to write to this bit, write “0”. The value, if read in
event counter mode, turns out to be indeterminate.
Nothing is assigned (i = 1, 2, 4, 5).
In an attempt to write to this bit, write “0”. The value, if read, turns out
to be indeterminate.