ST7FMC1K2B3 STMICROELECTRONICS [STMicroelectronics], ST7FMC1K2B3 Datasheet - Page 201

• Manufacturer Part Number: ST7FMC1K2B3
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

MOTOR CONTROLLER (Cont’d)
10.6.10.2 Functional Description
The 3 PWM signals are generated using a free-
running 12-bit PWM Counter and three 13-bit
Compare registers for phase U, V and W: MCM-
PU, MCMPV and MCMPW registers.
A fourth 12-bit register is needed to set-up the
PWM carrier frequency: MCMP0 register.
Each of these compare registers is buffered with a
preload register. Transfer from preload to active
registers is done synchronously with PWM counter
underflow or overflow depending on configuration.
This allows to write compare values without risks
of spurious PWM transitions.
The block diagram of the PWM generator is shown
on
10.6.10.3 Prescaler
The 12-bit PWM Counter clock is supplied through
a 3-bit prescaler to allow the generation of lower
PWM carrier frequencies. It divides F
..., 8 to get F
This prescaler is accessed through three bits
PCP[2:0] in MPCR register; this register is buff-
ered: the new value is taken into account after a
PWM update event.
Figure 118. Counting sequence in center-aligned and edge-aligned mode
Figure
center-aligned
edge-aligned
mode
mode
117.
mtc-pwm
.
0
0
T = PWM period, Value of 12-bit Compare 0 Register= 16
1
1
2
2
mtc
T
by 1, 2, 3,
.....
....
15
15
T
10.6.10.4 PWM Operating mode
The PWM generator can work in center-aligned or
edge-aligned mode depending on the CMS bit set-
ting in the MPCR register.
Figure 118
quence .
It offers also an 8-bit mode to get a full 8-bit range
with a single compare register write access by set-
ting the PMS bit in MPCR register.
The comparisons described here are performed
between the PWM Counter value extended to 13
bits and the 13-bit Compare register. Having a
compare range greater than the counter range is
mandatory to get a full PWM range (i.e. up to
100% modulation). This principle is maintained for
8-bit PWM operations.
■
In this operating mode, the PWM Counter counts
up to the value loaded in the 12-bit Compare 0 reg-
ister then counts down until it reaches zero and re-
starts counting up.
The PWM signals are set to ‘0’ when the PWM
Counter reaches, in up-counting, the correspond-
ing 13-bit Compare register value and they are set
to ‘1’ when the PWM Counter reaches the 13-bit
Compare value again in down-counting.
16
16
Center-aligned Mode (CMS bit = 1)
15
0
shows the corresponding counting se-
....
1
.....
2
ST7MC1xx/ST7MC2xx
16
1
0
0
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