UM0434 datasheet(358/390 Pages) STMICROELECTRONICS

358 / 390 page

UM0434

Nexus3 module

359/391

For branch history messages, I-CNT represents the number of instructions executed since

the last taken/non-taken direct branch, predicate instruction, last taken/not-taken indirect

branch, or exception. Branch instructions that trigger message generation are included in

the I-CNT. Instructions that generate history bits are not included in the I-CNT.

The sequential instruction counter overflows when its value reaches 255 and is reset to 0.

The next BTM message (corresponding to the 256th or later instruction) is converted to a

synchronization type message.

Program trace queueing

Nexus3 implements a programmable depth queue (a minimum of 32 entries is

recommended) for queuing all messages. Messages that enter the queue are transmitted

through the auxiliary pins in the order in which they are queued.

Note:

If multiple trace messages need to be queued at the same time, watchpoint messages have

the highest priority:

(WPM

→ OTM → BTM → DTM).

12.7.4

Program trace timing diagrams (2 MDO/1 MSEO Configuration)

Figure 74.

Program trace—indirect branch message (traditional)

Figure 75.

Program trace—indirect branch message (history)

TCODE = 4

Source processor = 0000

Number of sequential instructions = 128

Relative address = 0xA5

MCKO

MSEO_B

MDO[1:0]

TCODE = 28

Source processor = 0000

Number of sequential instructions = 0

Relative address = 0xA5

Branch history = 010100101 (w/ stop)

MCKO

MSEO_B

MDO[1:0]

UM0434 Datasheet(PDF) 358 Page - STMicroelectronics