.TH iverilog-fpga 1 "$Date: 2004/10/04 01:10:57 $" Version "$Date: 2004/10/04 01:10:57 $"
.SH NAME
iverilog-fpga - FPGA code generator for Icarus Verilog

.SH SYNOPSIS
.B iverilog -tfpga
[iverilog-options] sourcefile

.SH DESCRIPTION
.PP
The FPGA code generator supports a variety of FPGA devices, writing
EDIF output depending on the target. You can select the architecture
of the device, and the detailed part name. The architecture is used to
select library primitives, and the detailed part name is written into
the generated file for the use of downstream tools.

The code generator is invoked with the \-tfpga flag to iverilog. It
understands the part= and the arch= parameters, which can be set with
the \-p flag of iverilog:

	iverilog \-parch=virtex \-ppart=v50\-pq240\-6 \-tfpga foo.vl

This example selects the Virtex architecture, and give the detailed
part number as v50\-pq240\-6. The output is written into a.out unless a
different output file is specified with the \-o flag.


.SH OPTIONS
\fIiverilog \-tfpga\fP accepts the following options:
.TP 8
.B -parch=\fIfamily\fP
The \fIfamily\fP setting further specifies the target device
family. See FPGA FAMILIES below.

.TP 8
.B -ppart=\fIdevice\fP
This specifies a specific device in the form of a detailed part
number. The format of this number is defined by the part vendor. In
most cases, the device string is taken literally and written as is to
the EDIF output.

.SH "FPGA FAMILIES"

The following is a list of architecture types that this code generator
supports.

.TP 8
.B lpm
This is a device independent format, where the gates are device types
as defined by the LPM 2 1 0 specification. Some backend tools may take
this format, or users may write interface libraries to connect these
netlists to the device in question.

The \fBlpm\fP family is the default if no other is specified.
.TP 8
.B virtex
If this is selected, then the output is formatted as an EDIF 2 0 0 file,
suitable for Virtex class devices. This is supposed to know that you
are targeting a Virtex part, so can generate primitives instead of
using external macros. It includes the VIRTEX internal library, and
should work properly for any Virtex part.
.TP 8
.B virtex2
If this is selected, then the output is EDIF 2 0 0 suitable for
Virtex\-II and Virtex\-II Pro devices. It uses the VIRTEX2 library, but
is very similar to the Virtex target.

.SH "EDIF ROOT PORTS"

The EDIF format is explicit about the interface into an EDIF file. The
code generator uses that control to generate an explicit interface
definition into the design. (This is *not* the same as the PADS of a
part.) The generated EDIF interface section contains port definitions,
including the proper direction marks.

With the (rename ...) s\-exp in EDIF, it is possible to assign
arbitrary text to port names. The EDIF code generator therefore does
not resort to the mangling that is needed for internal symbols. The
base name of the signal that is an input or output is used as the name
of the port, complete with the proper case.

However, since the ports are single bit ports, the name of vectors
includes the string "[0]" where the number is the bit number. For
example, the module:

.nf
	module main(out, in);
	    output out;
	    input [2:0] in;
	    [...]
	endmodule
.fi

creates these ports:

.nf
	out   OUTPUT
	in[0] INPUT
	in[1] INPUT
	in[2] INPUT
.fi

Target tools, including Xilinx Foundation tools, understand the []
characters in the name and recollect the signals into a proper bus
when presenting the vector to the user.

.SH "PADS AND PIN ASSIGNMENT"

The ports of a root module may be assigned to specific pins, or to a
generic pad. If a signal (that is a port) has a PAD attribute, then
the value of that attribute is a list of locations, one for each bit
of the signal, that specifies the pin for each bit of the signal. For
example:

.nf
        module main( (* PAD = "P10" *) output out,
                     (* PAD = "P20,P21,P22" *) input [2:0] in);

            [...]

        endmodule
.fi

In this example, port ``out'' is assigned to pin 10, and port ``in''
is assigned to pins 20\-22. If the architecture supports it, a pin
number of 0 means let the back end tools choose a pin. The format of
the pin number depends on the architecture family being targeted, so
for example Xilinx family devices take the name that is associated
with the "LOC" attribute.

NOTE: If a module port is assigned to a pin (and therefore attached to
a PAD) then it is *not* connected to a port of the EDIF file. This is
because the PAD (and possibly IBUF or OBUF) would become an extra
driver to the port. An error.

.SH "SPECIAL DEVICES"

The code generator supports the "cellref" attribute attached to logic
devices to cause specific device types be generated, instead of the
usual device that the code generator might generate. For example, to
get a clock buffer out of a Verilog buf:

.nf
	buf my_gbuf(out, in);
	$attribute(my_buf, "cellref", "GBUF:O,I");
.fi

The "cellref" attribute tells the code generator to use the given
cell. The syntax of the value is:

.nf
	<cell type>:<pin name>,...
.fi

The cell type is the name of the library part to use. The pin names
are the names of the type in the library, in the order that the logic
device pins are connected.

.SH EXAMPLES

.TB 8
.I COMPILING WITH XILINX FOUNDATION/ISE
Compile a single-file design with command line tools like so:

.nf
	% iverilog \-parch=virtex \-o foo.edf foo.vl
	% edif2ngd foo.edf foo.ngo
	% ngdbuild \-p v50\-pq240 foo.ngo foo.ngd
	% map \-o map.ncd foo.ngd
	% par \-w map.ncd foo.ncd
.fi

.SH "AUTHOR"
.nf
Steve Williams (steve@icarus.com)

.SH SEE ALSO
iverilog(1),
.BR "<http://www.icarus.com/eda/verilog/>"

.SH COPYRIGHT
.nf
Copyright \(co  2003 Stephen Williams

This document can be freely redistributed according to the terms of the
GNU General Public License version 2.0