AN2525 Freescale Semiconductor / Motorola, AN2525 Datasheet - Page 13

• Manufacturer Part Number: AN2525
• Description: DC Motor - XOR version TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

Synchronization
signal for DC Motor
– XOR version
(DCmXor_sync)
Synchronized Change
of PWM Prescaler
And Synchronization
Signal Prescaler
MOTOROLA
The DCmXor_sync TPU function uses information obtained from DCmXor_C
and DCmXor_T 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 DCmXor_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 DCmXor_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
DC Motor – XOR version TPU Function Set (DCmXor)
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
Detailed Function Description
center_time
center_time
T
T
AN2525/D
13