UM0434 datasheet(351/390 Pages) STMICROELECTRONICS

351 / 390 page

Nexus3 module

UM0434

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Branch history saves bandwidth and keeps consistency between methods of program trace,

yet may lose temporal order between BTM messages and other types of messages. Since

direct branches are not messaged, but are instead included in the history field of the indirect

branch history message, other types of messages may enter the FIFO between branch

history messages. The development tool cannot determine the ordering of events that

occurred with respect to direct branches simply by the order in which messages are sent

out.

Traditional BTM messages maintain their temporal ordering because each event that can

cause a message to be queued enters the FIFO in the order it occurred and is messaged

out maintaining that order.

12.7.2

BTM message formats

The e200z3 Nexus3 block supports three types of traditional BTM messages: direct,

indirect, and synchronized messages. It supports two types of branch history BTM

messages: indirect branch history, and indirect branch history with synchronized messages.

Debug status messages and error messages are also supported.

Indirect branch messages (History)

Indirect branches include all taken branches whose destination is determined at run time,

interrupts, and exceptions. If DC1[PTM] is set, indirect branch information is messaged out

in the format shown in

Table 247:

Indirect branch messages (Traditional)

If DC1[PTM] is cleared, indirect branch information is messaged out in the format shown in

Table 248:

Direct branch messages (Traditional)

Direct branches, conditional or unconditional, are all taken branches whose destinations are

fixed in the instruction opcode. Direct branch information is messaged out in the format

shown in

Table 249:

Table 247.

Indirect Branch Message (History) Format

(1–32 bits)

(1–8 bits)

(4 bits)

(6 bits)

Branch History

Relative Address

Sequence

Count

Source

Proces

TCODE

(011100

)

Maximum length = 82 bit; Minimum length = 13 bits

Table 248.

Indirect Branch Message Format

(1–32 bits)

(1–8 bits)

(4 bits)

(6 bits)

Relative Address

Sequence Count

Source

Process

TCODE

(000100)

Maximum length = 50 bits; minimum length = 12 bits

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