72
Memory Controller
7.4
DDR Layout Guidelines
The following sections provide layout information for 80331 DDR333 configuration.
7.4.1
Source Synchronous Signal Group
The guidelines below are for the source synchronous signal group which includes Data bits
DQ
,
check bits
CB
, data mask
DM
, and
DQS
associated strobe.
The 80331 source synchronous signals are divided into groups consisting of data bits
DQ
and
check bits
CB
. There is an associated strobe
DQS
for each
DQ
,
DM
and
CB
group. When data
masking is not used system memory
DM
pins on the DDR needs to be tied to ground. The grouping
is as follows for the different memory configurations:
Table 32.
x64 DDR Memory Configuration
Data Group
Associated Strobe
DQ[7:0], DM[0]
DQS0
DQ[15:8], DM[1]
DQS1
DQ[23:16], DM[2]
DQS2
DQ[31:24], DM[3]
DQS3
DQ[39:32], DM[4]
DQS4
DQ[47:40], DM[5]
DQS5
DQ[55:48], DM[6]
DQS6
DQ[63:56], DM[7]
DQS7
Table 33.
x72 DDR Memory Configuration
Data Group
Associated Strobe
DQ[7:0], DM[0]
DQS0
DQ[15:8], DM[1]
DQS1
DQ[23:16], DM[2]
DQS2
DQ[31:24], DM[3]
DQS3
DQ[39:32], DM[4]
DQS4
DQ[47:40], DM[5]
DQS5
DQ[55:48], DM[6]
DQS6
DQ[63:56], DM[7]
DQS7
CB[7:0]
,
DM[8]
DQS8
Summary of Contents for 80331
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