AN2514 Freescale Semiconductor / Motorola, AN2514 Datasheet - Page 17

• Manufacturer Part Number: AN2514
• Description: 3-Phase Sine Wave Generator TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

Synchronization
signal for 3-Phase
Sine Wave
Generator
(3Sin_sync)
MOTOROLA
LH_C7 state lasts 32 IMB clock cycles (see
10 IMB clock cycles. The service starts immediately after the top channel high
to low transition, which occurs at a period of DT before the bottom channel low
to high transition (see
IMB clock cycles – DT. The 3Sin functions are designed so that no other 3Sin
state can request service at this time. The MPW, in the case when only 3Sin
functions are running on one TPU, is then
and has a minimum value of at least 12 IMB clock cycles (when latency = 0).
Note that the MPW, as well as the DT, are not entered into the parameter
RAM in IMB clock cycles, but in TCR1 clock cycles. It is recommended for
the 3Sin function that the TCR1 clock is configured for its maximum speed,
which is the IMB clock divided by 2. In this case the MPW = 27 – DT, with a
minimum value of 6.
When other functions are running concurrently on the same TPU, the longest
state of each function with its time-slot transition can increase the calculated
MPW value. The 3Sin_fault function does not affect the MPW. The 3Sin_sync,
if used, increases the MPW value by 22 (44 IMB clock cycles). The 3Sin_res,
if used, increases the MPW value by 20 (40 IMB clock cycles).
If a lower value than the one calculated, is set for the MPW parameter, the
motion system can run with a higher motor voltage amplitude, but with a risk,
that the dead-time is not maintained.
It is also possible to use the Worst-Case Latency (WCL), which 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 3Sin PWM
channels. Convert the number, from IMB clock cycles to TCR1 clock cycles, to
get the MPW.
The 3Sin_sync TPU function uses information obtained from 3Sin 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.
3-Phase Sine Wave Generator TPU Function Set (3Sin)
= 32 IMB clock cycles + 10 IMB clock cycles – DT + 12 IMB clock cycles =
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Figure
latency + 12 IMB clock cycles =
= 54 IMB clock cycles – DT
6), so that the latency is 32 IMB clock cycles + 10
Table
9). Its time slot transition is
Detailed Function Description
AN2514/D
17