Ecc Coding; 64-Bit Ecc Coding Scheme; Tlsb Data Wrapping - DEC AlphaServer 8200 Technical Manual

Table 2-5

TLSB Data Wrapping

2.2.8.6

ECC Coding

Data is protected using quadword ECC. The 256-bit data bus is divided
into four quadwords. Protection is allocated as follows:
Figure 2-3 shows the ECC coding scheme for TLSB_D<63:0> and
TLSB_ECC<7:0>. The same coding scheme is used for each of the other
three quadwords, and again for the four quadwords in the second data cy-
cle.
Figure 2-3

64-Bit ECC Coding Scheme

DATA 6666 5555
BITS 3210 9876
XOR S7 0000 0000
XOR S6 1111 1111
1111 1111
XOR S5
XOR S4 1100 0000
0011
1000
XNOR S3
1010 0110-
XNOR S2
0001 0101
XOR S1
1011 0100
XOR S0
7766 6666
HEX
50DB 8742
SYNDROME
CHECK
BITS 7654 3210
XOR S7 1000 0000
XOR S6 0100 0000
0010 0000
XOR S5
XOR S4 0001 0000
XNOR S3 0000
1000
XNOR S2
0000 0100
XOR S1
0000 0010
XOR S0
0000 0001
HEX
8421 0000
SYNDROME
0000 8421
TLSB_ADR<5>
0
0
1
1
• TLSB_D<63:0> is protected by TLSB_ECC<7:0>
• TLSB_D<127:64> is protected by TLSB_ECC<15:8>
• TLSB_D<191:128> is protected by TLSB_ECC<23:16>
• TLSB_D<255:192> is protected by TLSB_ECC<31:24>
5555 5544 4444 4444 3333
5432 1098 7654 3210 9786
1111 1111 1111 1111 0000
0000 0000 0000 0000 1111
0000 0000 1111 1111 0000
1111 1100 1100 0000 1111
1110 0011 0011 1000 1110
1001 1001 1010 0110 1001
0101 0111 0001 0101 0101
1101 0001 1011 0100 1101
9999 9988 BBAA AAAA
5555
DB87 42AF 50DB 8742 DB87
Data Cycle
0
1
0
1
3322 2222 2222
3333 1111
5432 1098 7654 3210 9876
1111 1111 0000
0000 0000
1111 1111 1111 0000 0000
1111 1111 0000
1111 0000
1100 0000 1111
1100 1100
0011 1000 1110
0011 0011
1010 0110
1001 1001 1001
0001 0101 0101
0111 0111
0100 1011 0010
0001 1110
FFEE EEEE 1111
5544 1100
41CA 9653 CA96
42AF 53BE
Data Bytes
0–31
32–63
32–63
0–31
1111 11
5432 1098
7654 3210
0000 0000 1111 1111
0000
0000 1111 1111
1111 1111 0000 0000
1100 0000 1111 1100
0011 1000 1110 0011
1010 0110 1001 1001
0001 0101 0101 0111
0100 1011 0010 1110
3322 2222 DDDD DDCC
41CA 9653 CA98 53BE
BXB0824.AI
TLSB Bus 2-21