The Tektronix 156-2622-00 is a Serial Data Interface controller monolithic integrated circuit used in 11000-series mainframes. It was designed by Jim Peterson.
It is implemented as a semi-custom ASIC based on an HMOS process. One 156-2622-00 handles the SDI channels for all three plug-in bays.
The 156-2622-00 also decodes the quadrature signals from the rotary encoders on the front panel.