iopadmap - technology mapping of i/o pads (or buffers)

yosys> help iopadmap

iopadmap [options] [selection]

Map module inputs/outputs to PAD cells from a library. This pass
can only map to very simple PAD cells. Use 'techmap' to further map
the resulting cells to more sophisticated PAD cells.

-inpad <celltype> <in_port>[:<ext_port>]

Map module input ports to the given cell type with the
given output port name. if a 2nd portname is given, the
signal is passed through the pad cell, using the 2nd
portname as the port facing the module port.

-outpad <celltype> <out_port>[:<ext_port>]

-inoutpad <celltype> <io_port>[:<ext_port>]

Similar to -inpad, but for output and inout ports.

-toutpad <celltype> <oe_port>:<out_port>[:<ext_port>]

Merges $_TBUF_ cells into the output pad cell. This takes precedence
over the other -outpad cell. The first portname is the enable input
of the tristate driver, which can be prefixed with `~` for negative
polarity enable.

-tinoutpad <celltype> <oe_port>:<in_port>:<out_port>[:<ext_port>]

Merges $_TBUF_ cells into the inout pad cell. This takes precedence
over the other -inoutpad cell. The first portname is the enable input
of the tristate driver and the 2nd portname is the internal output
buffering the external signal.  Like with `-toutpad`, the enable can
be marked as negative polarity by prefixing the name with `~`.

-ignore <celltype> <portname>[:<portname>]*

Skips mapping inputs/outputs that are already connected to given
ports of the given cell.  Can be used multiple times.  This is in
addition to the cells specified as mapping targets.

-widthparam <param_name>

Use the specified parameter name to set the port width.

-nameparam <param_name>

Use the specified parameter to set the port name.

-bits

create individual bit-wide buffers even for ports that
are wider. (the default behavior is to create word-wide
buffers using -widthparam to set the word size on the cell.)

Tristate PADS (-toutpad, -tinoutpad) always operate in -bits mode.