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geda:icarus_xilinx_hints [2012/02/20 15:14] (current)
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 +====== Xilinx Hints ======
 +<​code>​For those of you who wish to use Icarus Verilog, in combination with
 +the Xilinx back end (Foundation or Alliance), it can be done.  I have
 +run some admittedly simple (2300 equivalent gates) designs through this
 +setup, targeting a Spartan XCS10.
  
 +Verilog:
 +
 +   Older versions of Icarus Verilog (like 19990814) couldn'​t synthesize
 +   logic buried in procedural (flip-flop) assignment. ​ Newer versions
 +   (like 20000120) don't have this limitation.
 +
 +   ​Procedural assignments have to be given one at a time, to be
 +   "​found"​ by xnfsyn. ​ Say
 +       ​always @ (posedge Clk) Y = newY;
 +       ​always @ (posedge Clk) Z = newZ;
 +   ​rather than
 +       ​always @ (posedge Clk) begin
 +           Y = newY;
 +           Z = newZ;
 +       end
 +
 +   ​Steve'​s xnf.txt covers most buffer and pin constructs, but I had reason
 +   to use a global clock net not connected to an input pin.  The standard
 +   ​Verilog for a buffer, combined with a declaration to turn that into a
 +   BUFG, is:
 +       buf BUFG( your_output_here,​ your_input_here );
 +       ​$attribute(BUFG,"​XNF-LCA","​BUFG:​O,​I"​)
 +
 +   I use post-processing on my .xnf files to add "​FAST"​ attributes to
 +   ​output pins.
 +
 +Running ivl:
 +
 +   The -F switches are important. ​ The following order seems to robustly
 +   ​generate valid XNF files, and is used by "​verilog -X":
 +      -Fsynth -Fnodangle -Fxnfio
 +
 +Generating .pcf files:
 +
 +   The ngdbuild step seems to lose pin placement information that ivl
 +   puts in the XNF file.  Use xnf2pcf to extract this information to
 +   a .pcf file, which the Xilinx place-and-route software _will_ pay
 +   ​attention to.  Steve says he now makes that information available
 +   in an NCF file, with -fncf=<​path>,​ but I haven'​t tested that.
 +
 +Running the Xilinx back end:
 +
 +   You can presumably use the GUI, but that doesn'​t fit in Makefiles :-).
 +   Here is the command sequence in pseudo-shell-script:​
 +      ngdbuild -p $part $1.xnf $1.ngd
 +      map -p $part -o map.ncd $1.ngd
 +      xnf2pcf <$1.xnf >​$1.pcf ​   # see above
 +      par -w -ol 2 -d 0 map.ncd $1.ncd $1.pcf
 +      bitgen_flags = -g ConfigRate:​SLOW -g TdoPin:​PULLNONE -g DonePin:​PULLUP \
 +                     -g CRC:enable -g StartUpClk:​CCLK -g SyncToDone:​no \
 +                     -g DoneActive:​C1 -g OutputsActive:​C3 -g GSRInactive:​C4 \
 +                     -g ReadClk:​CCLK -g ReadCapture:​enable -g ReadAbort:​disable
 +      bitgen $1.ncd -l -w $bitgen_flags
 +
 +   The Xilinx software has diarrhea of the temp files (14, not including
 +   .xnf, .pcf, .ngd, .ncd, and .bit), so this sequence is best done in a
 +   ​dedicated directory. ​ Note in particular that map.ncd is a generic name.
 +
 +   I had reason to run this remotely (and transparently within a Makefile)
 +   via ssh.  I use the gmake rule
 +%.bit : %.xnf
 +        ssh -x -a -o '​BatchMode yes' ${ALLIANCE_HOST} \
 +               ​remote_alliance ${REMOTE_DIR} $(basename $@) 2>&1 < $<
 + scp ${ALLIANCE_HOST}:​${REMOTE_DIR}/​$@ .
 +    and the remote_alliance script (on ${ALLIANCE_HOST})
 +/bin/csh
 +cd $1
 +cat >! $2.xnf
 +xnf2pcf <$2.xnf >! $2.pcf
 +./backend $2
 +
 +   There is now a "​Xilinx on Linux HOWTO" at
 +         ​http://​www.polybus.com/​xilinx_on_linux.html
 +   I haven'​t tried this yet, it looks interesting.
 +
 +Downloading:​
 +
 +   I use the XESS (http://​www.xess.com/​) XSP-10 development board, which
 +   uses the PC parallel (printer) port for downloading and interaction
 +   with the host.  They made an old version of their download program
 +   ​public domain, posted it at
 +      http://​www.xess.com/​FPGA/​xstools.zip ,
 +   and now there is a Linux port at
 +      ftp://​ftp.microux.com/​pub/​pilotscope/​xstools.tar.gz .
 +
 +The above hints are based on my experience with Foundation 1.5 on NT
 +(gack) and Alliance 2.1i on Solaris. ​ Your mileage may vary.  Good luck!
 +
 +     - Larry Doolittle ​  <​LRDoolittle@lbl.gov> ​  ​August 19, 1999
 +                                        updated February 1, 2000
 +</​code>​
geda/icarus_xilinx_hints.txt ยท Last modified: 2012/02/20 15:14 (external edit)