MAC7200 datasheet(253/976 Pages) FREESCALE

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Functional Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

175

tools can determine which bit is the end of the history information. The pre-loaded bit itself is not part of

the history, but is transmitted with the packet.

A value of one (1) is shifted into the history buffer on a taken direct branch (conditional or unconditional)

and on any instruction whose predicate condition resolved as true. A value of zero (0) is shifted into the

history buffer on any instruction whose predicate condition executed as false as well as on branches not

taken. This will include indirect as well as direct branches not taken.

11.11.2.3.4

Sequential Instruction Count (I-CNT)

The I-CNT packet, is present in all BTM Messages. For traditional Branch Messages (Thumb mode only),

I-CNT represents the number of sequential ARM7 instructions, or non-taken branches in between

Direct/Indirect Branch Messages.

For Branch History Messages in Thumb mode, I-CNT represents the number of ARM7 instructions

executed since the last taken/non-taken direct branch, last taken indirect branch or exception. Not taken

indirect branches are considered sequential instructions and cause the instruction count to increment. For

Branch History Messages in ARM mode, I-CNT also represents the number of ARM7 instructions

executed since the last predicate instruction.

The sequential instruction counter overflows when its value reaches 255. The next BTM Message

following an instruction counter overflow will be converted to a synchronization type message.

NOTE

When an undefined instruction causes an exception, the undefined

instruction itself will be included in the BTM instruction count.

11.11.2.3.5

Program Trace Queueing

A7S Nexus3 implements a programmable depth queue (32 minimum entry recommended) for queuing all

messages. Messages that enter the queue are transmitted via the auxiliary pins in the order in which they

are queued.

11.11.2.4 Program Trace Timing Diagrams (2 MDO / 1 MSEO configuration)

Figure 11-35. Program Trace – Indirect Branch Message (Traditional)

TCODE = 4

source processor = 0000

# of sequential instructions = 128

relative address = 8'ha5

MCKO

MSEO_B

MDO[1:0]

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