AN2367 Freescale Semiconductor / Motorola, AN2367 Datasheet - Page 10

• Manufacturer Part Number: AN2367
• Description: Using the Multiphase Motor Commutation TPU Function (COMM)with the MPC500 Family
• Manufacturer: Freescale Semiconductor / Motorola

COMM Function Example
Sensorless Match Update Mode
3
Like all TPU functions, the performance limit of the COMM function in a given application is dependent
on the service time (latency) of other active TPU channels. This is due to the way the scheduler operates.
Worst case latency in any TPU application can be closely estimated. To analyze the performance of an
application that appears to approach the limits of the TPU, use the guidelines given in the TPU reference
manual, the information from the state time table below and the figures from the state timing tables of the
other active TPU functions.
Since COMM will always be used in conjunction with at least two other TPU functions - an input function
and a PWM function - the overall proposed system must be analyzed to assess the possible performance.
Section 7 of TPUPN09 provides detailed notes on performance and use of the COMM function.
3.1
The following example shows how the COMM function can be configured to work with the HALLD
function (in sensored mode).
Table 2 shows a possible state table for a three-phase motor using sensored mode and HALLD.
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NOTE: Execution times do not include the time slot transition time (TST= 10 or 14 CPU clocks)
1. Call tpu_comm_init_sensorless_match to select the required TPU channels for the COMM function
2. Initialize the QDEC or FQD function.
3. Call tpu_comm_force_state to set the COMM channels to the required initial commutation-state.
4. Call tpu_enable (defined in mpc500.c and supplied with the standard header files) to set the TPU
5. Wait for the appropriate bits in the TPU HSRR0 register to clear. This can be checked by calling
6. Fetch the position count value from the FQD or QDEC channels and calculate the initial upper and
7. Call tpu_comm_upper, tpu_comm_lower and tpu_comm_offset to initialise upper, lower and
8. Call tpu_comm_start_update. The COMM function now runs in sensorless mode, accessing the
S1 FORCE_COMM
S2 UPDATE_COMM
S3 MATCH_UPDATE_COMM
and initialize counter_addr, the comm_states array, update_period and no_of_pins.
master COMM channel to the required priority.
tpu_get_hsr (defined in mpc500.c and supplied with the standard header files).
lower parameter values.
offset.
QDEC or FQD channels as required.
State Number & Name
Use and Performance of the COMM Function
COMM Function Example
Using the Multiphase Motor Commutation TPU Function
Freescale Semiconductor, Inc.
Table 1. Commutation Function—State Timing
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24 + (14 * NO_OF_PINS)
64 + (14 * NO_OF_PINS)
62 + (14 * NO_OF_PINS)
Max. CPU Clock Cycles
RAM accesses by TPU
16
16
5
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