AN2518 Freescale Semiconductor / Motorola, AN2518 Datasheet - Page 14

• Manufacturer Part Number: AN2518
• Description: 3-Phase Sine Wave Generator - 3 outputs version - XOR version TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

AN2518/D
Synchronization
signal for 3-Phase
Sine Wave
Generator – 3
outputs version –
XOR version
(3Sin3Xor_sync)
Synchronized Change
of PWM Prescaler
And Synchronization
Signal Prescaler
14
3-Phase Sine Wave Generator – 3 outputs version – XOR version TPU Function Set (3Sin3Xor)
The 3Sin3Xor_sync TPU function uses information obtained from 3Sin3Xor_R
and 3Sin3Xor_T 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.
The 3Sin3Xor_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 3Sin3Xor_R function at
the time the PWM parameters are reloaded. 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 signal 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,
|move|
|move|
Figure 6. Synchronization signal adjustment examples
center_time
center_time
center_time
center_time
T
T
T
T
Go to: www.freescale.com
pw
pw
|move|
|move|
pw
pw
center_time
center_time
center_time
center_time
center_time
center_time
T
T
T
T
T
T
center_time
center_time
T
T
MOTOROLA