AR# 46723


Zynq-7000 SoC - Can I swap PS DDR DQ pins for board design?


Can I swap DQ pins for the memory controller, or are they fixed?



UG933 contains the following information:

"Byte and bit swapping is allowed to facilitate PCB routing, except for LPDDR2,which specifically forbids swapping. When swapping bits, keep all bits within the same byte group."

What this means is that pin numbers can be swapped between Zynq and the SDRAM within abyte, or entire byte groups can be switched. 

Since these pins are fixedon Zynq there is nothing you can do to swap these within Zynq or Vivado.

Instead, you would need to physically route different numbered pins together onthe board.

For example, this could be done in cases where routing is much easier if DDR3 pins DQ[2] and DQ[7] could be switched. 

Since this is allowed, it is possible to route pin DQ[2] from Zynq to DQ[7] of the memory and viceversa. 

Since data will be returned the same way it was sent out of the Zynq PHY interface, physically swapping data lines between Zynq and memory will have no net effect on the data.


Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
53051 Zynq-7000 SoC - PS DDR Controller N/A N/A
AR# 46723
Date 05/23/2018
Status Active
Type General Article
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