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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
137
Intel XScale
®
Processor—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
3.6.13.2
Trace Buffer Usage
The trace buffer for the IXP45X/IXP46X network processors is 256 bytes in length. The
first byte read from the buffer represents the oldest trace history information in the
buffer. The last (256th) byte read represents the most recent entry in the buffer. The
last byte read from the buffer will always be a message byte. This provides the
debugger with a starting point for parsing the entries out of the buffer. Because the
debugger needs the last byte as a starting point when parsing the buffer, the entire
trace buffer must be read (256 bytes on IXP45X/IXP46X network processors) before
the buffer can be parsed.
is a high level view of the trace buffer.
Figure 20.
Indirect Branch Entry Address Byte Organization
B4346-01
target[31:24]
target[23:16]
target[15:8]
target[7:0]
indirect br msg
Trace buffer is read by
software in this
direction. The message
byte is always the last of
the 5 bytes in the entry
to be read.
Figure 21.
High-Level View of Trace Buffer
B4347-01
target[7:0]
1001 CCCC (indirect)
1000 CCCC (direct)
1100 CCCC (direct)
. . .
1111 1111 (roll-over)
target[31:24]
target[23:16]
target[15:8]
target[7:0]
1101 CCCC (indirect)
1000 CCCC (direct)
1111 1111 (roll-over)
1000 CCCC (direct)
last byte read
(most recent entry)
first byte read
(oldest entry)
CHKPT1
CHKPT0