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M16C/28 Group
Under development Preliminary specification
Specifications in this manual are tentative and subject to change.
12.2 Timer B
Rev.0.60 2004.02.01
page 105 of N
REJ09B0047-0060Z
Item
Specification
Count source
f1, f2, f8, f32, fC32
Count operation
Up-count
Counter value is transferred to reload register at an effective edge of mea-
surement pulse. The counter value is set to “000016” to continue counting.
Count start condition
Set TBiS (i=0 to 2) bit3 to “1” (= start counting)
Count stop condition
Set TBiS bit to “0” (= stop counting)
Interrupt request generation timing When an effective edge of measurement pulse is input1
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).
TBiIN pin function
Measurement pulse input
Read from timer
Contents of the reload register (measurement result) can be read by reading TBi register2
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.
12.2.3 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 12.2.3.1). Figure 12.2.3.1 shows TBiMR register in pulse period and pulse
width measurement mode. Figure 12.2.3.2 shows the operation timing when measuring a pulse period.
Figure 12.2.3.3 shows the operation timing when measuring a pulse width.
Table 12.2.3.1 Specifications in Pulse Period and Pulse Width Measurement Mode
Figure 12.2.3.1 TBiMR Register in Pulse Period and Pulse Width Measurement Mode
Timer Bi mode register (i=0 to 2)
Address
After reset
TB0MR to TB2MR
039B16 to 039D16
00XX00002
Bit name
Bit symbol
RW
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
(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.
Function
b3 b2
Count source
select bit
Timer Bi overflow
flag ( Note)
0 : Timer did not overflow
1 : Timer has overflowed
0 0 : f1 or f2
0 1 : f8
1 0 : f32
1 1 : fC32
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.
RW
RO
TB0MR register
Must be set to “0” in pulse period and pulse width measurement mode
TB1MR, TB2MR registers
Nothing is assigned. When write, set to “0”. When read, its content turns out to be
indeterminate.