M16C29 Datasheet, PDF (145/499 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/Tiny SERIES

M16C/29 Group
12. Timer B
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 12.8). Figure 12.20 shows the TBiMR register in pulse period and pulse width
measurement mode. Figure 12.21 shows the operation timing when measuring a pulse period. Figure
12.22 shows the operation timing when measuring a pulse width.
Table 12.8 Specifications in Pulse Period and Pulse Width Measurement Mode
Item
Specification
Count source
f1, f2, f8, f32, fC32
Count operation
• Increment
• Counter value is transferred to reload register at an effective edge of mea-
Count start condition
surement pulse. The counter value is set to 000016 to continue counting.
Set TBiS (i=0 to 2) bit ⁽³⁾ 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 input ⁽¹⁾
• Timer overflow. When an overflow occurs, MR3 bit in the 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
Read from timer
Measurement pulse input
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 undefined until the second valid edge is input after the timer starts counting.
3. Bits TB0S to TB2S are assigned to the bit 5 to bit 7 in the TABSR register .
Timer Bi Mode Register (i=0 to 2)
b7 b6 b5 b4 b3 b2 b1 b0
10
Symbol
TB0MR to TB2MR
Address
039B16 to 039D16
After Reset
00XX00002
Bit Symbol
TMOD0
TMOD1
MR0
MR1
MR2
MR3
TCK0
TCK1
Bit Name
Function
RW
Operation mode
select bit
b1 b0
1 0 : Pulse period / pulse width
measurement mode
RW
RW
Measurement mode
select bit
b3 b2
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: Do not set.
RW
RW
TB0MR register
Set to 0 in pulse period and pulse width measurement mode
RW
TB1MR, TB2MR registers
Nothing is assigned. If necessary, set to 0. When read, its content is undefined
Timer Bi overflow
flag ⁽¹⁾
Count source
select bit
0 : Timer did not overflow
1 : Timer has overflowed
b7 b6
0 0: f1 or f2
0 1: f8
1 0: f32
1 1: fC32
RO
RW
RW
NOTE:
1.This flag is undefined after reset. When the TBiS bit is set to 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 by program. Bits TB0S to TB2S are assigned to the bit 5 to bit 7 in the TABSR register.
Figure 12.20 TBiMR Register in Pulse Period and Pulse Width Measurement Mode
Rev. 1.12 Mar.30, 2007 ^{page 121} of 458
REJ09B0101-0112