Nexus3/ Module
e200z3 Power Architecture Core Reference Manual, Rev. 2
10-32
Freescale Semiconductor
10.7.3
BTM Operation
10.7.3.1
Enabling Program Trace
Both types of branch trace messaging can be enabled in one of two ways:
•
Setting DC1[TM] to enable program trace
•
Using WT[PTS] to enable program trace on watchpoint hits. e200z3 watchpoints are configured
within the CPU.
10.7.3.2
Relative Addressing
The relative address feature is compliant with the IEEE-ISTO 5001-2003 standard recommendations and
is designed to reduce the number of bits transmitted for addresses of indirect branch messages.
The address transmitted is relative to the target address of the instruction that triggered the previous
indirect branch or synchronized message. It is generated by XORing the new address with the previous
address and then using only the results up to the most significant 1 bit in the result. To recreate this address,
an XOR of the most significant zero-padded message address with the previously decoded address gives
the current address. For the example given in
, assume the previous address
(A1) = 0x0003FC01, and the new address (A2) = 0x0003F365.
10.7.3.3
Execution Mode Indication
In order for a development tool to properly interpret instruction count and history information, it must be
aware of the execution mode context of that information. VLE instructions will be interpreted differently
from non-VLE instructions.
Program trace messages provide the execution mode status in the least significant bit of the reconstructed
address field. A value of zero indicates that preceding instruction count and history information should be
interpreted in a non-VLE context. A value of one indicates that the preceding instruction count and history
information should be interpreted in a VLE context. Note that when a branch results in an execution mode
Message Generation
A1
0000 0000 0000 0011 1111 1100 0000 0001
A2
0000 0000 0000 0011 1111 0011 0110 0101
A1
⊕
A2
0000 0000 0000 0000 0000 1111 0110 0100
M1
(Address Message)
1111 0110 0100
Address Re-creation
A1
0000 0000 0000 0011 1111 1100 0000 0001
M1
0000 0000 0000 0000 0000 1111 0110 0100
A1
⊕
M1 (A2)
0000 0000 0000 0011 1111 0011 0110 0101
Figure 10-27. Relative Address Generation and Re-Creation Example
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