Enhanced Time Processing Unit (eTPU2)
Freescale Semiconductor
29-57
PXR40 Microcontroller Reference Manual, Rev. 1
Figure 29-27. Time Slot Priority levels
29.3.3.2.1
Primary Scheme - Priority Among Channels on Different Levels
Although time slot priority assignment is fixed, the servicing priority is not. The primary scheme
acknowledges the priority level assigned to a time slot, granting service first to a channel having the same
priority. In
, time slot one has a high-level assignment; therefore, a high-level channel
requesting service is recognized first. However, if no high-level channel requests service, the Scheduler
recognizes a requesting middle-level channel. If this level has no request, the Scheduler continues to the
low-level. If no requests occur, the Scheduler truncates the seven state cycle and starts a new cycle at time
slot one, waiting for the first request. Granting service to a different-level channel is called priority passing.
The order of passing always gives the highest priority to the assigned level, and the second priority to the
higher of the remaining requesting priority levels as shown in
When priority is passed to another level, that level is serviced and the fixed-priority-level sequence is
resumed with the next time slot.
Table 29-17. Priority Passing
Assigned
Priority Level
Next
Priority Level
Next
Priority Level
High
Middle
Low
Middle
High
Low
Low
High
Middle
1
2
3
4
5
6
7
1
2
3
H
M
H
L
H
M
H
H
M
H
4
5
L
H
HIGH
MIDDLE
LOW
A
B
Summary of Contents for PXR4030
Page 1: ...PXR40 Microcontroller Reference Manual Devices Supported PXR4030 PXR4040 PXR40RM Rev 1 06 2011...
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Page 120: ...Signal Descriptions 3 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
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