108
Hardware Design Guide
IXP28XX Network Processor
MSF (SPI-4/CSIX/FC)
5.4
Package Trace Lengths for LVDS_Diff Signals
Table 38
provides package trace lengths for LVDS_Diff signals, listed by decreasing lengths. For
designs that implement dynamic deskew via training, matching of trace lengths through the
package is not required as the deskew logic will correct this mismatch. For designs that implement
static deskew, trace length-matching through the package may be required.
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 38
must be adjusted to
compensate for the difference in flight delay between the package and the PCB. For example
FC_RXCSRB_L has a package length of 0.597 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
0.597*(154/180) or 0.511 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.
Table 38.
Package Trace Lengths for LVDS_Diff 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)
FC_RXCSRB_L
15.168
0.597
SPI4_TDAT[15]
11.51
0.453
SPI4_TDAT[2]
8.628
0.340
FC_RXCSRB
15.167
0.597
SPI4_RDAT[2]
11.313
0.445
SPI4_TDAT_L[2]
8.623
0.339
SPI4_RDAT[0]
14.548
0.573
SPI4_RDAT_L[2]
11.312
0.445
FC_RXCDAT_L[3]
8.424
0.332
SPI4_RDAT_L[0]
14.546
0.573
SPI4_RDAT_L[10]
11.166
0.440
FC_RXCDAT[3]
8.42
0.331
FC_RXCSOF_L
14.46
0.569
SPI4_RDAT[10]
11.164
0.440
SPI4_TDAT[14]
7.807
0.307
FC_RXCSOF
14.455
0.569
FC_RXCDAT_L[2]
11.135
0.438
SPI4_TDAT_L[14]
7.807
0.307
SPI4_RDAT[4]
14.249
0.561
FC_RXCDAT[2]
11.133
0.438
SPI4_RCLK
7.721
0.304
SPI4_RDAT_L[4]
14.246
0.561
FC_TXCFC
11.018
0.434
SPI4_RCLK_L
7.717
0.304
FC_RXCDAT[0]
14.115
0.556
FC_TXCFC_L
11.013
0.434
SPI4_TDAT[13]
7.684
0.303
FC_RXCDAT_L[0]
14.114
0.556
SPI4_TPAR
10.961
0.432
SPI4_TDAT_L[13]
7.68
0.302
SPI4_RDAT[5]
13.928
0.548
SPI4_TPAR_L
10.953
0.431
SPI4_TDAT_L[5]
7.657
0.301
SPI4_RDAT_L[5]
13.928
0.548
FC_RXCPAR_L
10.769
0.424
SPI4_TDAT[5]
7.654
0.301
FC_RXCCLK_L
13.368
0.526
FC_RXCPAR
10.768
0.424
SPI4_RCTL
7.65
0.301
FC_RXCCLK
13.365
0.526
SPI4_TCLK_L
10.745
0.423
SPI4_RCTL_L
7.649
0.301
SPI4_TDAT_L[11]
12.978
0.511
SPI4_TCLK
10.744
0.423
SPI4_RDAT[11]
7.489
0.295
SPI4_TDAT[11]
12.976
0.511
SPI4_TCTL_L
10.595
0.417
SPI4_RDAT_L[11]
7.486
0.295
SPI4_TDAT_L[3]
12.947
0.510
SPI4_TCTL
10.591
0.417
FC_TXCCLK_L
7.436
0.293
SPI4_TDAT[3]
12.945
0.510
SPI4_TDAT_L[8]
10.226
0.403
FC_TXCCLK
7.435
0.293
FC_RXCFC_L
12.888
0.507
SPI4_TDAT[8]
10.222
0.402
SPI4_RDAT[8]
7.314
0.288
FC_RXCFC
12.883
0.507
SPI4_RDAT[14]
9.97
0.393
SPI4_RDAT_L[8]
7.311
0.288
FC_RXCDAT_L[1]
12.577
0.495
SPI4_RDAT_L[14]
9.968
0.392
FC_TXCDAT[2]
7.195
0.283
FC_RXCDAT[1]
12.573
0.495
SPI4_TDAT_L[10]
9.952
0.392
FC_TXCDAT_L[2]
7.195
0.283
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