AN2528 Freescale Semiconductor / Motorola, AN2528 Datasheet - Page 16

• Manufacturer Part Number: AN2528
• Description: Standard Space Vector Modulation TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

AN2528/D
Synchronization
signal for Standard
Space Vector
Modulation
(svmStd_sync)
16
Standard Space Vector Modulation TPU Function Set (svmStd)
When there are no channels of middle or low priority, simply leave out all the H
or L and the following TST or TST+4 from the formulas.
When the recommended configuration rules are not adhered to, the timing of
the worst case is considerably more complicated. It requires some familiarity
with the details of the TPU priority scheme. In this case, the Worst-Case
Latency (WCL), which is automatically calculated by the MPC500_Quick_Start
Graphical Configuration Tool, can serve as a good approximation. This is
always longer than the real-case. Let the WCL be calculated after the
configuration of TPU channels and then find the longest WCL value within all
svmStd PWM channels. Convert the number, from IMB clock cycles to TCR1
clock cycles, to get the MPW.
The svmStd_sync TPU function uses information obtained from svmStd PWM
functions, the actual PWM center times and the PWM periods. This allows a
signal to be generated, which tracks the changes in the PWM period and is
always synchronized with the PWM. The synchronization signal is a positive
pulse generated repeatedly after the prescaler or presc_copy PWM periods
(see next paragraph). The low to high transition of the pulse can be adjusted
by a parameter, either negative or positive, to go a number of TCR1 TPU cycles
before or after the PWM period center time. The pulse width pw is another
synchronization signal parameter.
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Convert MPW in IMB clock cycles to MPW in TCR1 clock cycles based
on TCR1 prescaler settings.
In case two the MPW is (according to
TST + H + TST + max(M,L) + TST+4 + HL
that is 40 + H + max(M,L) IMB clock cycles.
MPW (in IMB clock cycles) = 40 + H + max(M,L)
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Figure
8)
MOTOROLA