Transparent Mode
10.2.4
Error Reporting
By default the status pins will be the xor of actual data from the DRAM and expected
data from the tester. The AMB also stores 144 bits of DQ data. If the LGFBITS control
bit is cleared the 144 bits of data will be actual data read from the DRAM. Otherwise
the result of the data compare is stored. In either case the tester must still provide
expected data for the AMB to properly set the status pins.
Normally the test will stop when an error occurs. It is the responsibility of the tester or
test program to track errors, read error registers and stop or continue as appropriate.
This may require multiple iterations of the same test to execute, collect data and re-
start the test.
10.2.4.1
Multiple Failures
There are some implications if multiple failures occur in the same DRAM burst. Three
control register bits determine how these failures should be captured. If the log first fail
(lgffail) bit is zero (default) the AMB will record only the last failure in a burst. When
the bit is set the AMB will record the first failure at the burst position matching the
burst position (bstpos) setting. If the bit is set and an error is logged, no further
logging will occur until the bit is cleared.
a) If a failure is detected only in one half of the burst (first and second or third and
fourth data words), the error pins will indicate which DRAM or DRAMs failed. The error
register will indicate which data lines failed and in which data words.
b) If a failure is detected in both halves of the burst (data word 1 or 2 and words 3 or
4), data from the second failure would overwrite data from the first failure. By default
this is prevented by the log fail bit. The error pins will continue to operate correctly. If it
is desired to collect data from a specific portion of the burst the burst position bits can
be used to select an appropriate burst position to record. For a 4 bit burst it is possible
to select data from the first or second half of the burst. For an 8 bit burst there are four
positions to choose from. These mappings are illustrated in the following figure.
Table 10-3. Mapping of Burst Position Bits to Error Capture
Log First Fail
Burst Position
BL=4
Bit0
0
Bit1
Bit0
x
1
2
3
4
x
0
0
144 bits*
144 bits
or 144 bits*
1
0
1
1
144 bits
Log First Fail
Burst Position
BL=8
Bit0
0
Bit1
x
Bit0
x
1
2
3
4
5
6
7
8
144 bits*
144 bits
or 144 bits*
or 144 bits*
or 144 bits*
1
0
0
1
1
1
0
1
144 bits
1
1
0
1
144 bits
144 bits
* The last failure will be saved in whatever burst position it occurs.
106
Intel® 6400/6402 Advanced Memory Buffer Datasheet
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