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ML66517 Family User’s Manual
Chapter 10
3-Phase PWM Function
10 – 27
10.4.1.3 Dead Time Timer (DTMn: n = 1, 2, 3) Operation (No Operation in Mode 2)
The dead time timers (DTMn: n = 1, 2, 3) operate as down-counters with a one-shot pulse output. If the output of
the size comparator that is comparing the contents of PW3C and PW3nR (n = U, V, W) changes, DTMn (n = 1,
2, 3) will begin operation 2 CPUCLK (2 cycles of the CPUCLK) later.
When the contents of the dead time timer register (DTMR) are loaded into DTMn (n = 1, 2, 3 ), the one-shot
pulse output begins and the DTMn (n = 1, 2, 3) count downward with the count clock selected by PW3CON1.
The one-shot pulse output is completed when DTMn (n = 1, 2, 3) becomes 00H (underflow). DTMn (n = 1, 2, 3)
is halted at FFH.
If the output of the size comparator changes during DTMn (n
= 1, 2, 3) operation, the contents of DTMR are
reloaded into DTMn (n = 1, 2, 3) and downward counting begins (the dead time timer is restarted).
If the 3-phase PWM counter (PW3C) is halted during DTMn (n = 1, 2, 3) operation, the DTMn (n = 1, 2, 3) is
also halted, and the contents are left unchanged.
An example of DTM1 operation in mode 1 and changes in the outputs of pins PWMU and PWMUB is described
below. (Operation is similar for DTM2 and the PWMB and PWMVB pins, and for DTM3 and the PWMW and
PWMWB pins.) Figure 10-18 shows a simplified diagram of the relation between dead time and changes in the
pin output. Figure 10-19 shows an example of the activation timing when the count clocks of both the 3-phase
PWM counter (PW3C) and DTM1 are 1/1 CPUCLK. Figure 10-20 shows an operation example at completion of
the dead time. Figure 10-21 shows an example of the activation timing when the count clock of the 3-phase
PWM counter (PW3C) is 1/1 CPUCLK and the DTM1 count clock is 1/4 CPUCLK.
[Note]
If a count clock other than CPUCLK is selected as the count clock for DTMn (n = 1, 2, 3), the dead time may
decrease by a maximum amount of (1 dead time clock – 1 CPUCLK).
Figure 10-18
Relation between Dead Time and Pin Output Change
PW3CYR contents
PW3C contents
0000H
DTM1 one-shot
pulse output
PWMU output
PWMUB output