Mips Technologies R4000 - Page 447

MIPS R4000 Microprocessor User's Manual 417
Error Checking and Correcting
The following example uses data with several 1-value bits: Data(63:0) =
0x0000 0000 0000 0043.
1. Expand the data to its binary equivalent in order to generate the
ECC check bits.
0x0000 0000 0000 0043 has 1s in the last byte only. The last byte
binary value is: 0x43 = 0100 0011
2
.
column # 7654 3210
0x0043 = 0100 0011
2
Since only columns 0, 1, and 6 have 1s, they are the only columns
that can generate the even parity bits.
2. Using Figure 16-1, generate even parity for the ECC check codes
in columns 0, 1, and 6:
Column 0 ECC Column 1 ECC Column 6 ECC Parity (even)
00 0 0
00 0 0
01 0 1
10 0 1
00 1 1
00 1 1
11 0 0
11 1 1
3. This parity value, 0011 1100
2
, is sent out over the ECC(7:0) check
bus.