READI Module
MPC561/MPC563 Reference Manual, Rev. 1.2
24-38
Freescale Semiconductor
24.8
Program Trace
This section details the program trace mechanism supported by READI for the RCPU. Program trace is
implemented via branch trace messaging (BTM) as per the IEEE-ISTO 5001-1999 definition.
24.8.1
Branch Trace Messaging
Branch trace messaging facilitates program trace by providing the following types of information:
•
Messaging for taken direct branches includes how many sequential instructions were executed
since the last taken branch or exception. Direct (or indirect) branches not taken are counted as
sequential instructions.
•
Messaging for taken indirect branches and exceptions includes how many sequential instructions
were executed since the last taken branch or exception and the unique portion of the branch target
address or exception vector address.
•
For some mispredicted branches and exception occurrences, program trace correction messages
correct the number of instructions since last taken branch as transmitted in prior BTM message.
24.8.1.1
RCPU Instructions that Cause BTM Messages
The following RCPU instructions, when executed, cause indirect branch messages to be encoded:
1. Taken branch relative to link or counter registers
2. Context switching sequential instructions
3. Exception taken (error/interrupts)
The following RCPU instruction, when executed, causes direct branch messages to be encoded:
1. Taken direct branch instructions
24.8.2
BTM Message Formats
BTM messages are of five types — direct, indirect, correction, synchronization, and error.
24.8.2.1
Direct Branch Messages
Direct branches (conditional or unconditional) are all taken branches whose destination is fixed in the
instruction opcode.
The program trace direct branch message has the following format:
Figure 24-19. Direct Branch Message Format
TCODE (3)
Sequence Count
[1 - 8 bits]
Max Length = 14 bits
[6 bits]
Min Length = 7 bits
Summary of Contents for MPC561
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