AN2524 Freescale Semiconductor / Motorola, AN2524 Datasheet - Page 14

• Manufacturer Part Number: AN2524
• Description: DC Motor with Dead-Time Correction TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

AN2524/D
Synchronization
signal for DC Motor
with Dead-Time
Correction
(DCmDt_sync)
Synchronized Change
of PWM Prescaler
And Synchronization
Signal Prescaler
14
DC Motor with Dead-Time Correction TPU Function Set (DCmDt)
You can also use the Worst-Case Latency (WCL) that is automatically
calculated by the MPC500_Quick_Start Graphical Configuration Tool. It can
serve as a good approximation of MPW. The calculated WCL is always longer
than the real-case is. Let the WCL be calculated after the configuration of the
TPU channels and then find the longest WCL value within all the DCmDt PWM
channels. Convert the number from IMB clock cycles to TCR1 clock cycles, to
get the MPW.
The DCmDt_sync TPU function uses information obtained from DCmDt PWM
functions, the actual PWM center times and the PWM periods. This allows a
signal to be generated, that 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 before or after the PWM
period center time of a number of TCR1 TPU cycles. The pulse width pw is
another synchronization signal parameter.
The DCmDt_sync TPU function actually uses the presc_copy parameter
instead of the prescaler parameter. The prescaler parameter holds the
prescaler value that is copied to the presc_copy by the DCmDt_bottom function
at the time of the PWM parameters reload. This ensures that new prescaler
values for the PWM signals, as well as the synchronization signal, are applied
at the same time. Write the synchronization signals prescaler parameter
address to the sync_presc_addr parameter to enable this mechanism. Write 0
to disable it, and remember to set the synchronization signal presc_copy
parameter instead of the prescaler parameter in this case.
move > 0
move > 0
prescaler = 1
prescaler = 1
move < 0
move < 0
prescaler = 2
prescaler = 2
Freescale Semiconductor, Inc.
For More Information On This Product,
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Figure 8. Synchronization signal adjustment examples
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