UM0434 datasheet(355/390 Pages) STMICROELECTRONICS

355 / 390 page

Nexus3 module

UM0434

356/391

The formats for program trace direct/indirect branch with synchronized messages and

indirect branch history with synchronized messages are shown in

Table 255:

Exceptions resulting in program trace synchronization are summarized in

Table 256.

Table 254.

Direct/Indirect branch with synchronization message format

(1–32 bits)

(1–8 bits)

(4 bits)

(6 bits)

Full Target Address

Sequence Count

Source

Process

TOCODE

(001011 or

001100)

Maximum length = 50 bits; minimum length = 12 bits

Table 255.

Indirect branch history with synchronization message format

(1–32 bits)

(1–8 bits)

(4 bits)

(6 bits)

Branch History

Full Target Address

Sequence

Count

Source

Process

TCODE

(011101)

Maximum length = 82 bit; Minimum length = 13 bits

Table 256.

Program trace exception summary

Exception

condition

Exception handling

System reset

negation

At the negation of JTAG reset,

j_trst_b, queue pointers, counters, state machines,

and registers within the Nexus3 module are reset. Upon the first branch out of

system reset, if program trace is enabled, the first program trace message is a

direct/indirect branch with synchronization message.

Program trace

enabled

The first program trace message, after program trace has been enabled, is a

synchronization message.

Exit from low

power/debug

Upon exit from a low-power mode or debug mode, the next direct/indirect branch

is converted to a direct/indirect branch with synchronization message.

Queue overrun

An error message occurs when the message queue is full and a new message

cannot be queued. The FIFO discards messages until it has completely emptied

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

indicates which types of messages attempted to be queued while the FIFO was

being emptied. The next BTM message in the queue is a direct/indirect branch

with synchronization message.

Periodic program

trace

synchronization

A forced synchronization occurs periodically after 255 program trace messages

have been queued. A direct/indirect branch with synchronization message is

queued. The periodic program trace message counter then resets.

Event in

If the Nexus module is enabled, assorting

nex_evti_b initiates a direct/indirect

branch with synchronization 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 may be executed), a forced synchronization occurs. The

sequential counter then resets. A program trace direct/indirect branch with

synchronization message is queued upon execution of the next branch.

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