sky130_fd_io: Initial documentation only release.

The SKY130 IO cells is a toolkit IP. It contains all the cells and
primitives required to construct an I/O ring in the SKY130 technology.

This sky130_fd_io library contained in this document covers different
kinds of I/O cells,

 * a general purpose I/O (`sky130_fd_io__gpio`), and
 * a special I/O (`sky130_fd_io__sio`),
 * a reference generator (`sky130_fd_io__refgen`) for providing voltage
   references to the `sky130_fd_io__sio`, and
 * Power and Ground (PG) cells that make up the I/O ring.

Signed-off-by: Tim 'mithro' Ansell <>
32 files changed