OBSOLETE: Xilinx Document Navigator is Live (latest version is 1.2 as of July 26, 2011)

This blog is OBSOLETE now that the new DocNav 2012.2 is now part of  IDS release.

Update:
March, 2012: added a "Tips and Tricks" section.
August, 2011: Watch Xilinx Document Navigator 1.2 Overview Video 

Xilinx Document Navigator is an awesome document manager that

• downloads all HW (UG, AppNotes, errata, etc) and SW documents from one "Download" button
• automatically checks for updates on all documents
• can easily filter, find and search all documents
• With improvements made to "User Documents" tab in v1.2 that allow documents/URLs to be organized hierarchically and re-ordered (see the snapshot at the end), DocNav can now be used to manage ALL your documents, not just Xilinx documents. 

FFT v8.0 AXI with scaled output

The output of the FFT core can be set to "Scaled" to save some logic resources if the full precision is not required. A few things are worth mentioning to get the scaling to work:

SysGen Example of FFT v8.0 with AXI

Starting in IDS 12.3, most, if not all, new/upgraded Xilinx IP cores will only use AXI as user interface. For FFT v8.0 specifically, it provides AXI4-Stream interfaces for input/output data and control. The AXI4-stream interface is a lot simpler than memory mapped AXI4 interface. It uses basic handshake between the master and slave as shown in the snapshot below from the FFT v8.0 Data Sheet (note that all AXI IP cores have separate data sheets than the non-AXI versions). The key thing to remember is that the AXI payload is only transferred when both TVALID and TREADY are high.

I updated the SysGen example in the blog FFT results from Matlab fft, Bit Accurate C model and SysGen FFT block with FFT v8.0 core to show the use of  AXI4 stream interface. Below is the updated SysGen model:

The updated SysGen model and m file can be downloaded from here. Again, you will need to download the bit accurate model from FFT core web site yourself to run fft_compare.m script.

Understand maximum frequency reporting in XST

Let's say your design has a single 50MHz clock source coming in. It then goes to a DCM or PLL to generate three clock outputs at 50MHz, 100MHz and 150MHz. When you run through synthesis XST reports the maximum frequency of the design like below.

Use Excel to Draw Waveforms

I learned a trick yesterday from a friend's tweet that Excel can be used to draw waveforms using different cell border outlines. I just tried it out and within a few minutes I got a pretty nice waveform in front of me. There is no learning curve involved and no need to purchase and/or install a special waveform drawing tool. I presume OpenOffice Calc can be used to do the same thing.

Below is the waveform in Excel:

And here how it looks like in "Print Preview":