sky130/custom/sky130_fd_io/mag/README

This directory contains standard format files for "sky130_ef_io",
which is an efabless addendum to the SkyWater I/O library "sky130_fd_io".

sky130_ef_io does the following:

(1) Changes the orientation of the corner pad from upper-right to
    lower-left with a wrapper cell called "sky130_fd_io__corner_pad".  Also
    extends the power buses to make the dimensions of the corner pad
    multiples of 1um.

(2) Adds a 1um-wide spacer cell to complement the existing 5um-wide
    spacer cell.

(3) Adds wrappers for all the combinations of power pad base cell +
    power pad overlay, to create all 12 combinations, for pads with
    either high- or low-voltage clamps, connecting to one of the six
    power domains vddio, vdda, vccd, vssio, vssa, or vssd.

(4) Adds overlay cells that connect the clamps to the different domains,
    in four commonly-used configurations.

(5) Adds wrappers for specfic combinations of power pad base cells +
    power pad overlay + clamp connection overlay, to create 8 common
    combinations.

(6) (5/28/2021) Added a separate wrapper cell for the top_power_hvc_wpadv2
    cell for the "caravan" project to triple up metal to the pad for
    high current supply applications.  The clamp and the pad remain
    unconnected.

"sky130_ef_io" is open source copyright 2020 efabless, Inc.
Released under Apache 2.0 license

NOTES:
-------------------
Copy these .mag sources to open_pdks/sky130/custom/sky130_fd_io/mag/
Generate GDS:
	load sky130_ef_io
	cif *hier write disable		;# there are no interactions
	gds library true		;# don't write top-level cell
	gds addendum true		;# don't write readonly cells
	gds write sky130_ef_io

and copy sky130_fd_io.gds to open_pdks/sky130/custom/sky130_fd_io/gds/.

For LEF views, use
	lef write -hide
and copy the resulting file to open_pdks/sky130/custom/sky130_fd_io/lef/.
***BUT*** Some of the views need editing:
(1) Move m4 obstruction in com_slice_Xum from 93.365 to 173.75 so that
    the area is empty for placing subcells in this area.
(2) Fix non-manhattan geometry in the corner of the corner cell.
(3) Erase labels on non-Manhattan shapes in sky130_fd_io__top_xres4v2
    before running "lef write -hide".

These two actions have been codified into the following scripts:
	generate_gds_lib.sh
	generate_lef_views.sh


MODIFICATIONS:
-------------------
3/30/2021:  Corrected the power pad layouts to differentiate between
	    the pad and the core (which are different nets).  Text
	    "_PAD" added to the net on the pad, and port numbers
	    modified to match the corrected CDL netlists in open_pdks.
	    Rewriting GDS with the most recent magic techfile also
	    corrects the port/text layer:purpose pairs.

5/28/2021:  Added power cell with extra-wide metal3 for the "caravan"
	    project.

6/16/2021:  Fixed the mix-up between the "clamped" and "clamped2" pads.
	    To be consistent with the verilog and SPICE, the .mag, .lef,
	    and .gds views all need to have the names "clamped" and
	    "clamped2" swapped.

6/24/2021:  Fixed cell top_power_hvc, which had a Y offset of -47um.

10/28/2021: Corrected an offset overlay on sky130_ef_io__vdda_hvc_pad.

6/8/2023:   Corrected an issue with the vccd_lvc_clamped3 and
	    vssd_lvc_clamped3 pads overdrawing the m3 resistor with
	    metal3 and via2, respectively.