Timer B
97
Mitsubishi microcomputers
M16C / 62N Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Item
Specification
Count source
f1, f8, f32, fC32
Count operation
Up count
Counter value “000016” is transferred to reload register at measurement
pulse's effective edge and the timer continues counting
Count start condition
Count start flag is set (= 1)
Count stop condition
Count start flag is reset (= 0)
Interrupt request generation timing When measurement pulse's effective edge is input (Note 1)
When an overflow occurs. (Simultaneously, the timer Bi overflow flag
changes to “1”. Assume that the count start flag condition is “1” and then the
timer Bi overflow flag becomes “1”. If the timer Bi mode register has a write-
access after next count cycle of the timer from the above condition, the timer
Bi overflow flag becomes “0”.)
TBiIN pin function
Measurement pulse input
Read from timer
When timer Bi register is read, it indicates the reload register’s content
(measurement result) (Note 2)
Write to timer
Cannot be written to
(3) Pulse period/pulse width measurement mode
In this mode, the timer measures the pulse period or pulse width of an external signal. (See Table 1.15.8.)
Figure 1.15.19 shows the timer Bi mode register in pulse period/pulse width measurement mode. Figure
1.15.20 shows the operation timing when measuring a pulse period. Figure 1.15.21 shows the operation
timing when measuring a pulse width.
Table 1.15.8. Timer specifications in pulse period/pulse width measurement mode
Figure 1.15.19. Timer Bi mode register in pulse period/pulse width measurement mode
Note 1: An interrupt request is not generated when the first effective edge is input after the timer has started counting.
Note 2: The value read out from the timer Bi register is indeterminate until the second effective edge is input
after the timer has started counting.
Timer Bi mode register
Symbol
Address
When reset
TBiMR(i=0 to 5)
039B16 to 039D16
00XX00002
035B16 to 035D16
00XX00002
Bit name
Bit symbol
W
R
b7
b6
b5
b4
b3
b2
b1
b0
Operation mode
select bit
1 0 : Pulse period / pulse width
measurement mode
b1 b0
TMOD1
TMOD0
MR0
Measurement mode
select bit
MR2
MR1
MR3
TCK1
TCK0
0
1
0 0 : Pulse period measurement (Interval between
measurement pulse's falling edge to falling edge)
0 1 : Pulse period measurement (Interval between
measurement pulse's rising edge to rising edge)
1 0 : Pulse width measurement (Interval between
measurement pulse's falling edge to rising edge,
and between rising edge to falling edge)
1 1 : Must not be set.
Function
b3 b2
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.
Count source
select bit
Timer Bi overflow
flag ( Note 1)
0 : Timer did not overflow
1 : Timer has overflowed
0 0 : f1
0 1 : f8
1 0 : f32
1 1 : fC32
b7 b6
Note 1: It is indeterminate when reset. Assume that the count start flag condition is “1” and then the timer Bi
overflow flag becomes “1”. If the timer Bi mode register has a write access after next count cycle of
the timer from the above condition, the timer Bi overflow flag becomes “0”. This flag cannot be set to
“1” by software.
Note 2: Timer B0, timer B3.
Note 3: Timer B1, timer B2, timer B4, timer B5.
0 (Must always be “0” in pulse period/pulse width measurement mode; i = 0, 3)
(Note 2)
(Note 3)