AutoFocus User’s Guide
46
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3.
Now compare this address to the one you would expect by looking at the
Data.List
window. Since
you executed a single step you would expect the address before the current PC location to be the
one transmitted on the trace port:
4.
You may need to perform a couple of single steps to see:
-
(a) if there is a logical error (pairs of trace signals are swapped) indicating an erroneous
pinout or
-
(b) if the errors seem to be related to certain trace signals being wrong every now and than.
For (b), timing violations could be the problem.
1 1000100 1 1010000
1 0000000 1 0000000
0 0010000
Trace packet bits can be structured as shown to the left.
Each eighth bit is set to one if a packet follows and is
cleared for the last packet.
1 1010000
1 1000100
1 0000000
1 0000000
0 0010000
Trace packet bits can be sorted as shown to the left.
101.0000
10.0010.0
0.0000.00
0000.000
001.0000
Dividing the row into groups of four bits (nibble) gives the
address in binary format. Since the address is transmitted
LSB first, this is done from right to left and top to bottom.
0101.0000
0010.0010
0000.0000
0000.0000
001
Now we write two nibbles per line again from right to left and
top to bottom. Bits[6:4] of the fifth packet of a full branch
address contain a reason code (here: 0x1 = “tracing has
been enabled”).
5 0
2 2
0 0
0 0
001
Finally the conversion to the hexadecimal format gives the
full address 0x00002250.
Program counter (PC)
