Nexus Development Interface (NDI)
31-46
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
31.14 BTM Operation
31.14.1 Enabling Program Trace
Both types of branch trace messaging can be enabled in one of two ways:
•
Setting the TM field of the DC1 register to enable program trace (DC1[TM])
•
Using the PTS field of the WT register to enable program trace on watchpoint hits (e200z7
watchpoints are configured within the CPU)
Program Trace Enabled
The first program trace message (after program trace has been enabled) is a
synchronization message.
Exit from Low Power/Debug
Upon exiting from the low power or debug modes, the next direct/indirect branch is
converted to a direct/indirect branch with sync. message.
Queue Overrun
An error message occurs when a new message cannot be queued due to the message
queue being full. The FIFO discards messages until the queue is completely empty. After
it is empty, an error message is queued. The error encoding indicates the message types
denied queueing while the FIFO was emptying. The next BTM message in the queue is
a direct/indirect branch with sync. message.
Periodic Program Trace Sync.
A forced synchronization occurs periodically after 255 program trace messages have
been queued. A direct/indirect branch with sync. message is queued. The periodic
program trace message counter then resets.
Event In
If the Nexus module is enabled, an EVTI assertion initiates a direct/indirect branch with
sync. message upon the next direct/indirect branch (if program trace is enabled and the
EIC bits of the DC1 register have enabled this feature).
Sequential Instruction Count
Overflow
When the sequential instruction counter reaches its maximum count (up to 255
sequential instructions can be executed), a forced synchronization occurs. The
sequential counter then resets. A program trace direct/indirect branch with sync.message
is queued upon execution of the next branch.
Attempted Access to Secure
Memory
For devices which implement security, any attempt to branch to secure memory locations
temporarily disables program trace and cause the corresponding BTM to be lost. The
following direct/indirect branch queues a direct/indirect branch with sync. message. The
count value within this message can be inaccurate since re-enabling program trace does
not guarantee alignment on an instruction boundary.
Collision Priority
All messages have the following priority: WPM
OTM
BTM
DTM. A BTM message
which attempts to enter the queue at the same time as a watchpoint message or
ownership trace message is lost. An error message is sent indicating the BTM was lost.
The following direct/indirect branch queues a direct/indirect branch with sync. message.
The count value within this message reflects the number of sequential instructions
executed after the last successful BTM message was generated. This count includes the
branch which did not generate a message due to the collision.
Table 31-26. Program Trace Exception Summary (continued)
Exception Condition
Exception Handling
Summary of Contents for PXR4030
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