New Users Forum

[bhathi123]

I'm very very new to this area...

I'm using a Spartan 3 development board.

I need to communicate with computer through RS232. (I have written the Verilog codes for RS232 Rx and Tx assuming a 25MHz input clock).  "Spartan 3E starter kit user guide" says FPGA pins for RS232 are "U8" and "M16". How can I use this information?

My verilog codes contain "initial" blocks. Since they are not synthesizable, I need to use some other method to initialize the modules. I thought of using an "init" port as an input in every module and initialization code is written in "always @(posedge init)" block. What I need to do is, drive the "init" port logic high at FPGA power up. Can I achive this? If yes what pin should I assign to the "init" input port?

Please help... Urgent

[eteam00 · Accepted solution]

The pin assignments for your S-3E Starter Kit board are declared in the .UCF file.  A reference .UCF file is included with the rest of the S-3E reference design files and guide documents which are readily available for download.

You should view this (downloadable) Xilinx training video which describes some basic FPGA design facilities and tools, including pin assignments.

Eventually you will want to learn more.  The reference document is UG625, the Constraints Guide.  Chapter 2 covers different methods of entering (or capturing) design constraints, including pin assignments and IO signaling standards and drive levels.

My verilog codes contain "initial" blocks. Since they are not synthesizable, I need to use some other method to initialize the modules.

This contradicts my understanding!  Suggest you spend a few minutes with the Synthesis and Simulation Design Guide UG626.  In version 13.4, discussion of 'Initial State' begins on page 62.

Finally, have you read the New Users Forum README thread?  Item #1 in this thread describes Document Navigator and how to download and install it.  Its use for Spartan-3 designs is a bit limited, but all the ISE design tools reference documents are included in the Doc Nav tool.  DocNav is a big help for locating and accessing the billions and billions of Xilinx documentation files.

-- Bob Elkind

[bhathi123]

Thank you very muach... It was very helpfull.. :)

[jpgore]

Thanks. Big help! Got me sorted.