Enhanced Time Processing Unit (eTPU2)
Freescale Semiconductor
29-83
PXR40 Microcontroller Reference Manual, Rev. 1
29.4.2.4.1
Worst-Case Assumptions and Formula
To estimate worst-case latency for a channel, assume this worst-case condition: the channel has just been
serviced in a time slot of its priority level, and all other channels in the system are continuously requesting
service and have cleared SGRs. The worst-case latency is the time from the end of the channel’s service
until the end of the channel’s next service. See
.
Figure 29-38. First-Pass Worst-Case Latency
To estimate worst-case latency:
•
Find the worst-case service time for each active channel.
•
Using the H-M-H-L-H-M-H time-slot sequence, map the channels that are granted for each time
slot.
•
Add time for six-clock time-slot transitions.
Finding the Worst-Case Service Time for Each Active Channel
A table for eTPU functions should list the longest threads (not counting initialization threads) for the
functions, and the number of eTPU SDM accesses in the longest thread (semaphored and non
semaphored). These figures will be used for estimating Microengine wait time.
is an example
for old TPU functions in which there are only simple SDM accesses. It does not take into consideration
the CDC operation and Microengine to Microengine communication.
The worst-case service time for each channel is: (CPCR=CCR=0)
Longest ((number of RAM accesses in longest 1) * RCR * 2 clocks). Note that the formula
adds 1 RAM accesses for the parameter preload that occurs during TST. There are actually three accesses
during TST, but only the first one can receive wait-states.
Table 29-21. Longest Threads and RAM Accesses for old TPU Functions
Function
Longest Thread RAM Accesses
DIO
10
4
ITC
40 (no linking)
42 (linking)
7
OC
40
7
PWM
24
4
Channel X
Serviced
Worst Case Latency Channel X
Other Channels Serviced
Channel X
Serviced Next
Summary of Contents for PXR4030
Page 1: ...PXR40 Microcontroller Reference Manual Devices Supported PXR4030 PXR4040 PXR40RM Rev 1 06 2011...
Page 30: ...PXR40 Microcontroller Reference Manual Rev 1 Freescale Semiconductor xxx...
Page 40: ...PXR40 Microcontroller Reference Manual Rev 1 xl Freescale Semiconductor...
Page 66: ...Memory Map PXR40 Microcontroller Reference Manual Rev 1 2 4 Freescale Semiconductor...
Page 120: ...Signal Descriptions 3 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Page 860: ...FlexCAN Module 24 50 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Page 1167: ...Decimation Filter Freescale Semiconductor 28 53 PXR40 Microcontroller Reference Manual Rev 1...
Page 1168: ...Decimation Filter 28 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
