Freescale Semiconductor MC9S12ZVM series, Reference Manual

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Chapter 1 Device Overview MC9S12ZVM-Family
MC9S12ZVM Family Reference Manual Rev. 1.3
62 Freescale Semiconductor
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Each control loop cycle is started by a PMF reload event. The PMF reload event restarts the PTU time
base. If the PTU is enabled, the reload is immediately passed through to the ADC and GDU modules.
The PMF generates the reload event at the required PWM reload frequency. The PMF reload event causes
the PTU time base to restart, to acquire the first trigger times from the list and the ADCs to start loading
the ADC conversion command from the Command Sequence List (CSL).
NOTE
In the PTU there is 7 bus cycle maximum time window after the reload
event assertion to access the first trigger times from the list. In this window
the trigger can not be generated. In the ADC there is 10 bus cycle maximum
time window after the
reload event assertion to access the first ADC
command from the list. In this window the ADC conversion can not be
started. If the measurement is control loop related these delays are
negligible due to much larger delays in the PWM-GDU-feedback loop.
When the trigger time is encountered the corresponding PTU trigger generates the trigger_x event for the
associated ADC. For simultaneous sampling the PTU generates simultaneous trigger_x events for both
ADCs. At the trigger_x event the ADC starts the first conversion of the next conversion sequence in the
CSL (the first ADC command is already downloaded).
A commutation event is used by the PMF to generate an async_reload event. The async_reload is used by
the PTU to update lists and re-initialize the trigger lists. If the PTU is enabled the async_reload is
immediately passed through to the ADC.
1.13.3.2 Control Loop Timing Considerations
Delays within the separate control loop elements require consideration to ensure correct synchronization.
Regarding the raw PWM signal as the starting point and stepping through the control loop stages, the
factors shown in
Figure 1-8 contribute to delays within the control loop, starting with the deadtime
Table 1-17. Control Loop Events
Device Level Event TIM PMF PTU ADC0 ADC1
commutation_event OC0
(1)
1. TIM channel OC0 must be configured to toggle on both edges.
commutation_event — — —
reload — reloada
(2)
2. PMF events reloadb and reloadc are not connected at device level
reload Restart Restart
async_reload — async_reload async_reload Seq_abort Seq_abort
trigger_0 — — trigger_0 Trigger —
trigger_1 — — trigger_1 — Trigger
glb_ldok — glb_ldok glb_ldok LoadOK LoadOK