UM0434 datasheet(348/390 Pages) STMICROELECTRONICS

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UM0434

Nexus3 module

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12.6.2

Ownership trace messaging (OTM)

Ownership trace information is messaged by means of the auxiliary port using OTM. For

e200z3 processors, there are two distinct methods for providing task/process ID data. Some

e200 processors contain a Book E–defined process ID register within the CPU while others

may not. Within Nexus, task/process ID data is handled in one of the following two ways in

order to maintain IEEE-ISTO 5001 compliance.

If the process ID register exists, it is updated by the operating system software to

provide task/process ID information. The contents of this register are replicated on the

pins of the processor and connected to Nexus. The process ID register value can be

accessed using the mfspr/mtspr instructions. See

Chapter 4.16.5: Process ID register

(PID0) on page 96.”

If the process ID register does not exist, the user base address register (UBA) is

implemented within Nexus. The UBA can be accessed by means of the JTAG/OnCE

port and contains the address of the ownership trace register (OTR). The memory-

mapped OTR is updated by the operating system software to provide task/process ID

information.

Note:

The e200z3 includes a process ID register (PID0), thus the UBA functionality is not

implemented.

There are two conditions that cause an ownership trace message:

When new information is updated in the OTR register or process ID register by the

e200z3 processor, the data is latched within Nexus and is messaged out through the

auxiliary port, allowing development tools to trace ownership flow.

When the periodic OTM message counter expires after 255 queued messages without

an OTM, an OTM is sent. The data is sent from either the latched OTR data or the

latched process ID data. This allows processors using virtual memory to be regularly

updated with the latest process ID.

Ownership trace information is messaged out in the format shown in

Table 243.

12.6.3

OTM error messages

An error message occurs when the message queue is full and a new message cannot be

queued. The FIFO discards incoming messages until it has completely emptied the queue.

Once the queue is emptied, an error message is queued. The error encoding indicates

which types of messages attempted to be queued while the FIFO was being emptied.

If only an OTM message attempts to enter the queue while the queue is being emptied, the

error message only incorporates the OTM error encoding 00000. If both OTM and either

BTM or DTM (that is, OTM and BTM or OTM and DTM) messages attempt to enter the

queue, the error message incorporates the OTM and program or data trace error

encoding 00111. If a watchpoint also attempts to be queued while the FIFO is being

emptied, then the error message incorporates error encoding 01000.

Table 243.

Ownership trace message format

(32 bits)

(4 bits)

(6 bits)

Task/Process ID Tag

Source

Process

TCODE

(000010)

Fixed Length = 42 bits

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