PXN20RM Datasheet, PDF (1238/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller

Nexus Development Interface (NDI)
NOTE
When DC[PTM] is set, direct branch messages are not transmitted. Instead,
each direct branch or predicated instruction toggles a bit in the history
buffer.
Resource Full Messages
The resource full message is used in conjunction with the branch history messages. The resource full
message is generated when the internal branch/predicate history buffer is full, or if the BTM Instruction
sequence counter (I-CNT) overflows. If synchronization is needed at the time this message is generated,
the synchronization is delayed until the next branch trace message that is not a resource full message.
The current value of the history buffer is transmitted as part of the resource full message. This information
can be concatenated by the tool with the branch/predicate history information from subsequent messages
to obtain the complete branch history for a message. The internal history value is reset by this message,
and the I-CNT value is reset as a result of a bit being added to the history buffer.
(1–32 bits)
(4 bits)
(4 bits)
(6 bits)
RDATA
RCODE
Src. Proc. TCODE (011011)
Max length = 46 bits; Min length = 15 bits
Figure 36-66. Resource Full Message Format
Table 36-59 shows the RCODE encodings and RDATA information used for Resource Full messages.
Table 36-59. RCODE Encoding
RCODE
Description
RDATA field
0000 Program Trace Instruction counter reached 255 and was reset. 0xFF
0001 Program Trace, Branch / Predicate Instruction History full.
Branch HIstory.
This type of packet is terminated by a stop bit set to
1 after the last history bit.
Program Correlation Messages
Program correlation messages are used to correlate events to the program flow that may not be associated
with the instruction stream. The following events result in a PCM when program trace is enabled:
• When the CPU enters debug mode, a PCM is generated. The instruction count and history
information provided by the PCM can be used to determine the last sequence of instructions
executed prior to debug mode entry.
• When the CPU enters a low power mode in which instructions are no longer executed, a PCM is
generated. The instruction count and history information provided by the PCM can be used to
determine the last sequence of instructions executed prior to low power mode entry.
• Whenever program trace is disabled by any means, a PCM is generated. The instruction count and
history information provided by the PCM can be used to determine the last sequence of instructions
executed prior to disabling program trace. A second PCM is generated on this event if there has
been an execution mode switch into or out of a sequence of VLE instructions. This VLE state
36-88
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor