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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
513 of 808
NXP Semiconductors
UM10360
Chapter 25: LPC17xx Motor Control PWM
8.6 Three-phase DC mode
The three-phase DC mode is selected by setting the DCMODE bit in the MCCON register.
In this mode, the internal MCOA0 signal can be routed to any or all of the MCO outputs.
Each MCO output is masked by a bit in the current commutation pattern register MCCP. If
a bit in the MCCP register is 0, its output pin has the logic level for the passive state of
output MCOA0. The polarity of the off state is determined by the POLA0 bit.
All MCO outputs that have 1 bits in the MCCP register are controlled by the internal
MCOA0 signal.
The three MCOB output pins are inverted when the INVBDC bit is 1 in the MCCON
register. This feature accommodates bridge-drivers that have active-low inputs for the
low-side switches.
The MCCP register is implemented as a shadow register pair, so that changes to the
active communication pattern occur at the beginning of a new PWM cycle. See
and
for more about writing and reading such registers.
shows sample waveforms of the MCO outputs in three-phase DC mode.
Bits 1 and 3 in the MCCP register (corresponding to outputs MCOB1 and MCOB0) are set
to 0 so that these outputs are masked and in the off state. Their logic level is determined
by the POLA0 bit (here, POLA0 = 0 so the passive state is logic LOW). The INVBDC bit is
set to 0 (logic level not inverted) so that the B output have the same polarity as the A
outputs. Note that this mode differs from other modes in that the MCOB outputs are
not
the opposite of the MCOA outputs.
In the situation shown in
, bits 0, 2, 4, and 5 in the MCCP register are set to
1. That means that MCOA1 and both MCO outputs for channel 2 follow the MCOA0
signal.