Chapter 13 Programmable Trigger Unit (PTUV2)
MC9S12ZVM Family Reference Manual Rev. 1.3
Freescale Semiconductor
483
error condition the trigger generator reloads the new data from the trigger list and starts to generate the
trigger. During an async reload event the TGxREIF interrupt flag is not set.
If the trigger value loaded from the memory contains double bit ECC errors (PTUDEEF flag is set) then
the data are ignored and the trigger generator reload error flag (TGxREIF) is not set.
13.4.5.5
Trigger Generator Timing Error
The PTU module requires minimum 6 core clock cycles to reload the next trigger values from the memory.
This reload time defines the minimum possible distance between two consecutive trigger values within a
trigger list or the distance between the reload event and the first trigger value.
The trigger generator timing error flag (TGxTEIF) is set if the loaded trigger value is smaller than the
current counter value. The execution of this trigger list is stopped until the next reload event. There are
different reasons for the trigger generator error condition:
•
reload time exceeds time of next trigger event
•
reload time exceeds the time between two consecutive trigger values
•
a subsequent trigger value is smaller than the predecessor trigger value
If the trigger value loaded from the memory contains double bit ECC errors (PTUDEEF flag is set) then
the data are ignored and the trigger generator timing error flag (TGxTEIF) is not set.
If enabled (TGxEIE is set) an interrupt will be generated.
13.4.5.6
Trigger Generator Done
The trigger generator done flag (TGxDIF) is set if the loaded trigger value contains 0x0000 or if the
number of maximum trigger events (32) was reached. Please note, that the time which is required to load
the next trigger value defines the delay between the generation of the last trigger and the assertion of the
done flag. If enabled (TGxDIE is set) an interrupt is generated.If the trigger value loaded from the memory
contains double bit ECC errors (PTUDEEF flag is set) then the data are ignored and the trigger generator
done flag (TGxDIF) is not set.
13.4.6
Debugging
To see the internal status of the trigger generator the register TGxLIST, TGxTNUM, and TGxTV can be
used. The TGxLIST register shows the number of currently used list. The TGxTNUM shows the number
of generated triggers since the last reload event. If the maximum number of triggers was generated then
this register shows zero. The trigger value loaded from the memory to generate the next trigger event is
visible inside the TGxTV register. If the execution of the trigger list is done then these registers are
unchanged until the next reload event. The next PWM reload event clears the TGxTNUM register and
toggles the used trigger list if PTULDOK was set.
To generate a reload event or trigger event independent from the PWM status the debug register bits
PTUFRE or TGxFTE can be used. A write one to this bits will generate the associated event. This behavior
is not available during stop or freeze mode.
