Mips Technologies R4000 - Tag ECC Generation

MIPS R4000 Microprocessor User's Manual 425
Error Checking and Correcting
Tag ECC Generation
The 25-bit tag ECC check matrix is similar to the 64-bit data check matrix;
the main difference is the number of check bits used and the manner in
which the errors are decoded. Figure 16-4 shows the check matrix for the
tag bits.
Figure 16-4 Check Matrix for the Tag ECC Code
NOTE: * This row indicates the number of 1s in the generated syndrome for each data
bit in error.
. 1. .
1. . .
. . 1.
. 1. .
1. . .
. . 1.
1111
ECC
Code
Bits
11
13
10
10
13
11
14
Number of
1s in
syndrome*
Data Bit
Check Bit 0
222
432
1. . .
. 1. .
1. . .
. 1. .
. . . 1
. . 1.
11. .
1. . .
. 1. .
. . . 1
. . 1.
1. . .
. 1. .
11. .
. . . 1
. . 1.
1. . .
. 1. .
1. . .
. 1. .
11. .
1111
1111
. . . .
1. . .
. 1. .
. . 1.
. . . 1
1. . .
1111
1111
. 1. .
. . . .
. . 1.
. . . 1
1. . .
. . . .
. 1. .
1111
1111
. . 1.
. . . 1
1. . .
. 1. .
. . 1.
. . . .
1111
1111
. . . 1
22
10
12
11
98
34
11
76
56
1111
5432
11
1098
7654 3210
3331 3311 3311 3311 3333 3333 3333 3333
MSB
LSB