M16C62_M Datasheet, PDF (121/615 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

Timers’ functions for three-phase motor control
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Triangular wave modulation
To generate a PWM waveform of triangular wave modulation, set “0” in the modulation mode select bit
(bit 6 at 034816). Also, set “1” in the timers A4-1, A1-1, A2-1 control bit (bit 1 at 034916). In this mode, each
of timers A4, A1, and A2 has two timer registers, and alternately reloads the timer register’s content to the
counter every time timer B2 counter’s content becomes 000016. If “0” is set to the effective interrupt
output specification bit (bit 1 at 034816), the frequency of interrupt requests that occur every time the timer
B2 counter’s value becomes 000016 can be set by use of the timer B2 counter (034D16) for setting the
frequency of interrupt occurrences. The frequency of occurrences is given by (setting; setting ≠ 0).
Setting “1” in the effective interrupt output specification bit (bit 1 at 034816) provides the means to choose
which value of the timer A1 reload control signal to use, “0” or “1”, to cause timer B2’s interrupt request to
occur. To make this selection, use the effective interrupt output polarity selection bit (bit 0 at 034816).
An example of U phase waveform is shown in Figure 1.15.6, and the description of waveform output
workings is given below. Set “1” in DU0 (bit 0 at 034A16). And set “0” in DUB0 (bit 1 at 034A16). In
addition, set “0” in DU1 (bit 0 at 034B16) and set “1” in DUB1 (bit 1 at 034B16). Also, set “0” in the effective
interrupt output specification bit (bit 1 at 034816) to set a value in the timer B2 interrupt occurrence
frequency set counter. By this setting, a timer B2 interrupt occurs when the timer B2 counter’s content
becomes 000016 as many as (setting) times. Furthermore, set “1” in the effective interrupt output specifi-
cation bit (bit 1 at 034816), set “0” in the effective interrupt output polarity select bit (bit 0 at 034816) and set
"1" in the interrupt occurrence frequency set counter (034D16). These settings cause a timer B2 interrupt
to occur every other interval when the U phase output goes to “H”.
When the timer B2 counter’s content becomes 000016, timer A4 starts outputting one-shot pulses. In this
instance, the content of DU1 (bit 0 at 034B16) and that of DU0 (bit 0 at 034A16) are set in the three-phase
output shift register (U phase), the content of DUB1 (bit 1 at 034B16) and that of DUB0 (bit 1 at 034A16)
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are set in the three-phase output shift register (U phase). After triangular wave modulation mode is se-
lected, however, no setting is made in the shift register even though the timer B2 counter’s content
becomes 000016.
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The value of DU0 and that of DUB0 are output to the U terminal (P80) and to the U terminal (P81)
respectively. When the timer A4 counter counts the value written to timer A4 (038F16, 038E16) and when
timer A4 finishes outputting one-shot pulses, the three-phase shift register’s content is shifted one posi-
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tion, and the value of DU1 and that of DUB1 are output to the U phase output signal and to U phase output
signal respectively. At this time, one-shot pulses are output from the timer for setting dead time used for
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setting the time over which the “L” level of the U phase waveform does not lap over the “L” level of the U
phase waveform, which has the opposite phase of the former. The U phase waveform output that started
from the “H” level keeps its level until the timer for setting dead time finishes outputting one-shot pulses
even though the three-phase output shift register’s content changes from “1” to “0” by the effect of the
one-shot pulses. When the timer for setting dead time finishes outputting one-shot pulses, "0" already
shifted in the three-phase shift register goes effective, and the U phase waveform changes to the "L"
level. When the timer B2 counter’s content becomes 000016, the timer A4 counter starts counting the
value written to timer A4-1 (034716, 034616), and starts outputting one-shot pulses. When timer A4 fin-
ishes outputting one-shot pulses, the three-phase shift register’s content is shifted one position, but if the
three-phase output shift register’s content changes from “0” to “1” as a result of the shift, the output level
changes from “L” to “H” without waiting for the timer for setting dead time to finish outputting one-shot
pulses. A U phase waveform is generated by these workings repeatedly. With the exception that the
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three-phase output shift register on the U phase side is used, the workings in generating a U phase
waveform, which has the opposite phase of the U phase waveform, are the same as in generating a U
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