Zynq ZedBoard User Manual page 9

CLK3) are used to represent the Micron device electrically furthest from 7Z020 (IC25). The
worksheet calculation results are shown in the following table.
Pin Group Length Length
(mm) (mils)
CLK0 55.77 2195.9
CLK1 55.77 2195.9
CLK2 41.43 1631.1
CLK3 41.43 1631.1
DQS0 51.00 2008.0
DQS1 50.77 1998.8
DQS2 41.59 1637.6
DQS3 41.90 1649.4
DQ[7:0] 50.63 1993.3
DQ[15:8] 50.71 1996.4
DQ[23:16] 40.89 1609.9
DQ[31:24] 40.58 1597.8
The DQS to CLK Delay fields in the PS7 DDR Configuration window should be populated using
the corresponding values from the previous table.
The configuration fields of the tool may not allow you to input a negative delay value, this is a
known problem with the 14.1 tools and scheduled for correction in the 14.2 tools release. In the
case of DQS2 and DQS3 fields for DQS to CLK Delay, simply enter a value of zero rather than
the negative delay values. This is an acceptable workaround since the calculated values are
relatively close to zero and the values provided in these fields are used as initial values for the
read/write training for DDR3. Keep in mind for LPDDR2 there is no write leveling, and for DDR2
there is no training whatsoever. In these memory use cases, the accuracy of the trace length info
is more important. This is covered in further detail in section 10.6.8 of the
UG585.
The Board Delay fields in the PS7 DDR Configuration window should be populated using the
corresponding values from the table above.
Table 2 - DDR3 Worksheet Calculations
Package Total
Length Length
(mils) (mils)
470 2665.9
470 2665.9
470 2101.1
470 2101.1
504 2512.0
495 2493.8
520 2157.6
835 2484.4
465 2458.3
480 2476.4
550 2159.9
780 2377.8
Figure 3 - DQS to Clock Delay Settings
Figure 4 - DDR3 Board Delay Settings
8
Propagation Total
Delay Delay
(ps/inch) (ns)
160 0.427
160 0.427
160 0.336
160 0.336
160 0.402
160 0.399
160 0.345
160 0.398
160 0.393
160 0.396
160 0.346
160 0.380
Xilinx Zynq TRM,
DQS to Board
CLK Delay
Delay (ns)
(ns)
0.025
0.028
-0.009
-0.061
0.410
0.411
0.341
0.358
1-Aug-2012