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On-chip terminatio in Altera Cyclone IV FPGA for DDR2 interface
von Ashish D. (Company: SLS) (ashishdevre)

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Hi All,
        I am dealing with the pin assignments specifications for 
Altera's Cyclone IV FPGA. I am using Altera's Quartus II software and 
using its QSYS tool I have designed a system to interface DDR2 SDRAM 
with FPGA. While I was assigning pin assignments to FPGA. I came across 
the feature - On-chip termination, which fascinated me as it can deduct 
the requirement of adding pull-up resistors and can reduce the bulkiness 
of the board.
       As all the pins from FPGA to SDRAM are output or bi-directional, 
I have applied output termination with series 50 ohms with calibration 
to all the pins. My questions are-
      1.Is my attempt of applying output termination, with series 50 
ohms calibration, to bi-directional pins correct?
         (I have read that
          For input pins, input termination should be used with parallel 
resistors
          For output pins output termination should be used with series 
resistors
          For bi-directional both the input and output termination or 
dynamic termination should be used.
         But in Cyclone IV input termination and dynamic termination 
options are not available. These options are there in Stratix family 
FPGAs)

     2. If output termination with series 5o ohm with calibration is 
correct, do I need to add any external resistors for termination on FPGA 
side?(Except RUP and RDN resistors)




Ashish Devre

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Re: On-chip termination in Altera Cyclone IV FPGA for DDR2 interface
von fpgaengineer (Guest)

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at first we should distinguish on chip termination for both FPGA and 
DDR2 chip, secondly oct does not necessarily eliminate the demand of 
external termination in all cases.

designing a ddr2/ddr3 interface requires attention at all parts of the 
design like ddr2 chip (number, position), fpga (oct options, si issues) 
and board design so different methods of termination can be applied 
according to the particular demands

before answering some of your particular questions seriously, some 
additional requirements should be provided

general information about handling of ddr issues can be taken from 
several sources of the inet like e.g. the ddr designers guide from 
micron, also altera and xilinx have ddr integration apps available

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