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  3. AR# 34153: Spartan-6 FPGA MCB - Can MCB pins be swapped to help facilitate board layout?

AR# 34153

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Spartan-6 FPGA MCB - Can MCB pins be swapped to help facilitate board layout?

描述

When interfacing between the MCB and an external SDRAM memory component, you must use the predefined MCP pin I/O locations.

The MIG tool generates a UCF to LOC the required pins properly.

However, to facilitate board layout, it might be desirable to swap MCB pins.

This Answer Record details the pins that can and cannot be swapped.

解决方案

Allowed Pin Swaps
 
  • DQ bit swapping at the memory interface.
    Swapping can only be done within a data-byte group.
     
  • Upper and lower byte lanes at an x16 memory interface.
    Swapping can only be done when the whole data-byte group, corresponding DQS pairs, and DM are swapped with each other.

Prevented Pin Swaps
 
  • Control pins (that is, RAS, CAS, WE, CKE, RESET, and ODT)
     
  • Address pins (BA and A) - The address pins are used to program mode registers during initialization.
    Also, bit A10 is used to control auto-precharge.
    These pins cannot be swapped.
     
  • UDM and LDM cannot be swapped as they correspond to the upper and lower data groups within the MCB and at the memory interface.
     
  • DQS differential pairs (DQS with DQS_n, UDQS with UDQS_n, LDQS with LDQS_n).
    DQS has specific requirements during the read and write operation as defined by JEDEC.
    Swapping these pairs would violate these requirements.
     
  • Upper and lower DQS pairs (UDQS/UDQS_n with LDQS/LDQS_N) as they correspond to the upper and lower data groups within the MCB and at the memory interface.
Additional Pin Rules
  • For pin information on RZQ and ZIO, please see (Xilinx Answer 34055).
     
  • The active-Low Chip Select (CS#) pin of the target memory device should be connected to ground on the board.
    Because the MCB only supports connections to a single memory component, it does not provide a signal to control the CS# input.
    If necessary, contact your memory vendor for more information.

链接问答记录

相关答复记录

Answer Number 问答标题 问题版本 已解决问题的版本
43318 MIG Spartan-6 MCB - How to Verify that Pin-out Requirements Are Met N/A N/A
40346 SP605 - Are the DQ pins for this board swappable? N/A N/A
43319 MIG Spartan-6 MCB - Clocking and Reset N/A N/A
35180 Spartan-6 - 12.4 Software Known Issues related to the Spartan-6 FPGA N/A N/A
34055 MIG Spartan-6 FPGA MCB - What are the requirements for the RZQ and ZIO pins? N/A N/A
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AR# 34153
日期 08/25/2014
状态 Active
Type 综合文章
IP
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