50
Hardware Design Guide
IXP28XX Network Processor
RDRAM
3.7
Package Trace Lengths for RDRAM Signals
Table 13
provides package trace lengths for RDRAM signals, listed by decreasing lengths in a
given logical grouping.
1
The flight time on the package substrate is 154ps/in which differs from the flight delay of standard
FR4, typical 180ps/in. As a result the package routing lengths in
Table 13
must be adjusted to
compensate for the difference in flight delay between the package and the PCB. For example
RDR0_CMD has a package length of 0.697 in, and the target PCB has a flight delay of 180ps/in. In
order to adjust the package length to match the PCB flight delay this length must be multiplied by
the ratio of 154/180 or the difference between the package and PCB flight delays. Therefore the
trace package routing length that must be accounted for on the PCB is 0.697*(154/180) or 0.596 in.
Note:
If the flight delay of the target PCB is not 180 ps/in then the ratio, (154/180), must be modified
accordingly, i.e., the denominator would be changed to reflect the actual flight delay.
1.
Signals in boldface type indicate the start of a logical grouping.
Table 13.
Package Trace Lengths for RDRAM Signals (Sheet 1 of 2)
Signal
Metric
Units
(mm)
English
Units
(in)
Signal
Metric
Units
(mm)
English
Units
(in)
Signal
Metric
Units
(mm)
English
Units
(in)
RDR0_CMD
17.709
0.697
RDR1_CTM
12.634
0.497
RDR2_DQA[3]
19.161
0.754
RDR0_DQB[8]
17.39
0.685
RDR1_CTMN
12.634
0.497
RDR2_DQA[0]
18.843
0.742
RDR0_DQB[5]
17.071
0.672
RDR1_DQA[2]
12.549
0.494
RDR2_DQA[8]
18.573
0.731
RDR0_RQ[3]
16.938
0.667
RDR1_CMD
12.436
0.490
RDR2_CTM
18.264
0.719
RDR0_DQB[2]
16.78
0.661
RDR1_DQA[6]
11.982
0.472
RDR2_CTMN
18.264
0.719
RDR0_RQ[0]
16.517
0.650
RDR1_DQA[0]
11.567
0.455
RDR2_DQA[6]
17.226
0.678
RDR0_DQB[6]
15.93
0.627
RDR1_DQB[8]
11.316
0.446
RDR2_DQA[4]
16.687
0.657
RDR0_RQ[5]
15.727
0.619
RDR1_DQB[7]
11.167
0.440
RDR2_DQA[1]
16.358
0.644
RDR0_SIO
15.466
0.609
RDR1_RQ[5]
10.884
0.429
RDR2_RQ[4]
16.105
0.634
RDR0_DQB[3]
15.411
0.607
RDR1_DQA[8]
10.782
0.424
RDR2_DQA[5]
16.087
0.633
RDR0_PCLKM
14.94
0.588
RDR1_DQB[4]
10.741
0.423
RDR2_RQ[0]
16.028
0.631
RDR0_SCK
14.294
0.563
RDR1_SCLKN
10.609
0.418
RDR2_DQA[7]
15.997
0.630
RDR0_DQB[1]
13.979
0.550
RDR1_RQ[0]
10.391
0.409
RDR2_DQA[2]
15.843
0.624
RDR0_RQ[2]
13.743
0.541
RDR1_DQA[4]
9.992
0.393
RDR2_CFM
15.645
0.616
RDR0_RQ[6]
13.651
0.537
RDR1_CFMN
9.67
0.381
RDR2_CFMN
15.645
0.616
RDR0_SCLKN
13.646
0.537
RDR1_CFM
9.668
0.381
RDR2_RQ[1]
15.448
0.608
RDR0_DQB[7]
13.607
0.536
RDR1_DQA[1]
9.603
0.378
RDR2_RQ[5]
15.271
0.601
RDR0_CTM
13.321
0.524
RDR1_RQ[1]
9.432
0.371
RDR2_RQ[7]
14.707
0.579
RDR0_CTMN
13.32
0.524
RDR1_DQB[5]
9.223
0.363
RDR2_RQ[2]
14.637
0.576
RDR0_DQA[2]
13.006
0.512
RDR1_RQ[3]
8.712
0.343
RDR2_DQB[4]
13.402
0.528
RDR0_DQA[5]
12.952
0.510
RDR1_SCK
8.639
0.340
RDR2_DQB[1]
13.239
0.521
RDR0_DQB[4]
12.898
0.508
RDR1_DQB[2]
8.627
0.340
RDR2_DQB[7]
13.103
0.516
RDR0_CFM
12.636
0.497
RDR1_DQB[1]
8.481
0.334
RDR2_DQB[3]
12.978
0.511
RDR0_CFMN
12.636
0.497
RDR1_PCLKM
8.465
0.333
RDR2_SIO
12.902
0.508
RDR0_DQB[0]
12.49
0.492
RDR1_DQA[5]
8.443
0.332
RDR2_RQ[6]
12.633
0.497
RDR0_DQA[6]
11.797
0.464
RDR1_DQA[7]
8.292
0.326
RDR2_DQB[8]
12.463
0.491
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