Timers (Timer B)
127
Mitsubishi microcomputers
M16C / 62P Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
development
Preliminary Specifications Rev.1.0
Specifications in this manual are tentative and subject to change.
Item
Specification
Count source
Count operation
f
1
, f
2
, f
8
, f
32
, f
C32
Up-count
Counter value is transferred to reload register at an effective edge of mea-
surement pulse. The counter value is set to “0000
16
” to continue counting.
Set TBiS (i=0 to 5) bit
3
to “1” (= start counting)
Set TBiS bit to “0” (= stop counting)
Interrupt request generation timing
When an effective edge of measurement pulse is input
1
Timer overflow. When an overflow occurs, MR3 bit of TBiMR register is set
to “1” (overflowed) simultaneously. MR3 bit is cleared to “0” (no overflow) by
writing to TBiMR register at the next count timing or later after MR3 bit was
set to “1”. At this time, make sure TBiS bit is set to “1” (start counting).
TBi
IN
pin function
Measurement pulse input
Read from timer
Contents of the reload register (measurement result) can be read by reading TBi register
2
Write to timer
Value written to TBi register is written to neither reload register nor counter
Notes:
1. Interrupt request is not generated when the first effective edge is input after the timer started counting.
2. Value read from TBi register is indeterminate until the second valid edge is input after the timer starts counting.
3. The TB0S to TB2S bits are assigned to the TABSR register bit 5 to bit 7, and the TB3S to TB5S bits are assigned
to the TBSR register bit 5 to bit 7.
Count start condition
Count stop condition
3. Pulse Period and Pulse Width Measurement Mode
In pulse period and pulse width measurement mode, the timer measures pulse period or pulse width of an
external signal (see Table 1.15.3). Figure 1.15.6 shows TBiMR register in pulse period and pulse width
measurement mode. Figure 1.15.7 shows the operation timing when measuring a pulse period. Figure
1.15.8 shows the operation timing when measuring a pulse width.
Table 1.15.3. Specifications in Pulse Period and Pulse Width Measurement Mode
Figure 1.15.6.
TBiMR Register in Pulse Period and Pulse Width Measurement Mode
Timer Bi mode register (i=0 to 5)
Symbol
Address
After reset
00XX0000
2
00XX0000
2
TB0MR to TB2MR
TB3MR to TB5MR
039B
16
to 039D
16
035B
16
to 035D
16
Bit name
Bit symbol
TMOD0
RW
RW
RW
b7
b6
b5
b4
b3
b2
b1
1
b0
0
Operation mode
select bit
1 0 : Pulse period / pulse width
measurement mode
b1 b0
TMOD1
MR0
Measurement mode
select bit
MR2
MR1
MR3
TCK1
TCK0
0 0 : Pulse period measurement
(Measurement between a falling edge and the
next falling edge of measured pulse)
0 1 : Pulse period measurement
(Measurement between a rising edge and the next
rising edge of measured pulse)
1 0 : Pulse width measurement
(Measurement between a falling edge and the
next rising edge of measured pulse and between
a rising edge and the next falling edge)
1 1 : Must not be set.
TB0MR and TB3MR registers
Must be set to “0” in pulse period and pulse width measurement mode
TB1MR, TB2MR, TB4MR, TB5MR registers
Nothing is assigned. When write, set to “0”. When read, its content turns out to be
indeterminate.
Function
b3 b2
Count source
select bit
Timer Bi overflow
flag ( Note)
0 : Timer did not overflow
1 : Timer has overflowed
0 0 : f
1
or f
2
0 1 : f
8
1 0 : f
32
1 1 : f
C32
b7 b6
Note: This flag is indeterminate after reset. When the TBiS bit = 1 (start counting), the MR3 bit is cleared to “0” (no overflow) by writing
to the TBiMR register at the next count timing or later after the MR3 bit was set to “1” (overflowed). The MR3 bit cannot be set to
“1” in a program. The TB0S to TB2S bits are assigned to the TABSR register's bit 5 to bit 7, and the TB3S to TB5S bits are
assigned to the TBSR register's bit 5 to bit 7.
RW
RW
RW
RW
RW
RO