Intel
®
81341 and 81342—DDR SDRAM Memory Controller
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
608
Order Number: 315037-002US
7.3.4.1
DDR ECC Generation
For write operations, the DMCU generates the error correction code which is written
along with the data. This section describes the operation of the DDR SDRAM Control
Block for ECC generation in a 64-bit wide memory and 64-bit region. The same
principles apply for 32-bit wide memory and in the 32-bit region in 64-bit wide
memory, however the DMCU generates 8-bit wide ECC by zero extending the data to
64-bits The algorithm for a write transaction is:
if data to write is 64 bits wide
Generate the ECC_with the G-matrix
Write the new data and ECC
else {Partial Write}
Read entire 64-bit data word from memory
Merge the new data portion with the data from memory
Generate the new ECC with the G-matrix
Write new data and ECC
shows how the data logically flows through the ECC hardware for a write
transaction.
The G-Matrix in
generates the ECC. The data to be written is input to the
matrix and the output is the ECC code. Each row of the G-Matrix indicates which data
bits of
AD[63:0]
needs to be XORed together to form the ECC bit. The resulting ECC
bits are driven on
CB[7:0]
.
Figure 91. DDR ECC Write Flow
A8159-01
Main
Memory
MCU
ECC
Memory
64-Bit Bus
Calculate ECC
with G-matrix
Data from Internal Bus