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how to replace simulation based delay in VHDL to make code synthesizable

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Newbie level 5
May 15, 2011
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i have made a block of OFDM in xilinx system generator which contains few delays then i translated the code in VHDL using the option in system generator. but that vhdl code contains delays that is made with after statement which is not synthesizable.

i have to run that code on extreme dsp kit but i am helpless.

is there any option to replace that delay code.
in my mode it is written in this way
d=q after 200 ps

i need a code to replace this delay code

Can you explain why you need the delays?
200 ps is too short to implement with a sequential circuit.
You can do short delays by routing the signal thru an extra LUT or by separating the source and destination a certain distance on the chip.
The precision will not be good, so it is better if you can do the design without the delays.

Delays are requirement of my design.... i need the synthesizable code. even i increased the delay but it gives timed out error on the hardware.

what is LUT.... actually i am new to VHDL and unable to nderstand all that too fast and time is short....

kindly come up with code if u can ..........

thanks in advance

---------- Post added at 01:19 ---------- Previous post was at 01:17 ----------

do u mean loop up table.........?

use a BUFD element: You should find it in your library for the paritiuclar device you are using for e.g. Spartan 3C or Virtex...etc.
You a for loop with a generate and create as many buffers components as you want.
Or simply repeat the component "n" time till you get your required delay in post layout sim

Depending on your target device you may be able to instantiate an I/O Delay primitive. Have a look through the vendors documentation to see if your FPGA has the capability. If so, they will typically provide example VHDL/Verilog code of how to instantiate the components.

in our code BUFT is used, is that sumthing related to BUFD....we are using Extreme development kit Virtex IV ....what should be the solution for that

---------- Post added at 06:59 ---------- Previous post was at 06:57 ----------

Blackhelicopter i didnt get what you are saying....can u explain with

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