Answers Database

XC5200: How to use Direct Connect routing resources?


Record #1618

Problem Title:
XC5200:	How to use Direct Connect routing resources?


Problem Description:
Keywords: XC5200, direct_connects,  CLB, IOBs

Urgency: Standard


Description

In order to increase the performance of an XC5200 design, there
are routing resources called direct connects which connect an
IOB to a neighboring CLB without going through regular routing
paths.	This would be the shortest routing delays that could
occur for data entering the chip.

How do I enable the software to use the direct connects?


Solution 1:

There currently are no switches or attributes to specify the
use of direct connects.

The easiest way to persuade the software to use direct connects
is to place timespecs on the design paths you wish to use this
routing resource.  If the timepsecs dictate the use of direct
connects, the software will subsequently place and route the
design accordingly.

For more information on using Timespecs, consult solution
numbers 1331, 1069, and 409.

Information may also be found in Chapter 4 of the Development
System Refence Guide Volume 1, which is defaultly installed
with the XACT 5.2.1/6.0.1 software and is availible from the
Xilinx Online Docs icons from the XACTstep 6.0 group.

This manual is also from the Xilinx FTP site at :

     ftp://ftp.xilinx.com/pub/documentation/dsref1.pdf



Solution 2:

If you find timespecs are ineffective, the next best thing you
can do is bring the mapped design into the XACT Floorplanner
and place the logic/FF next to the corresponding IOB you wish
to have the software route the direct connects.  By grouping
the logic with the IOB, the router is typically intelligent
enough to realize it can use the direct connects.

If you need information on using the floorplanner, there is
a tutorial that is defaultly installed by the XACT 5.2.1/6.0.1
software and may be accessed from the Learning Center icon
located in the XACTstep 6.0 group.  This Windows-based tutorial
is also accessible from the Xilinx FTP site :

     ftp://ftp.xilinx.com/pub/tutorials/xacttut.zip

Further information on the floorplanner may be found in the
Floorplanner Refernce Guide which also may be accessed from
the Xilinx Online Docs icon from the XACTstep 6.0 group.

This manual is also availible from the Xilinx FTP site at :

     ftp://ftp.xilinx.com/pub/documentation/floorpln.pdf



Solution 3:

If all else fails, the brute force method of using direct
connects is to hand route that particular portion using
Editlca, a Xilinx Design Editor (XDE) program.	Information
on using XDE may be found in Chapter 9 of the Development
System User Guide as well as Chapter 4 of the Development
System Reference Guide Volume 3.  Both are defaultly installed
by the XACT 5.2.1/6.0.1 software and may be accessed from
the Xilinx Online Docs icon from the XACTstep 6.0 group.

These manuals are also availible from the Xilinx FTP site :

     ftp://ftp.xilinx.com/pub/documentation/dsuser.pdf

     ftp://ftp.xilinx.com/pub/documentation/dsref3.pdf



Solution 4:





End of Record #1618