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Intel
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IXP42X product line and IXC1100 control plane processors—Intel XScale
®
Processor
Intel
®
IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor
DM September 2006
114 Order Number: 252480-006US
3.6.13.2 Trace Buffer Usage
IXP42X product line and IXC1100 control plane processors’ trace buffer 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 IXP42X product line and IXC1100
control plane processors) before the buffer can be parsed. Figure 23 is a high level view
of the trace buffer.
Figure 22. Indirect Branch Entry Address Byte Organization
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 23. High Level View of Trace Buffer
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