Power on die discovery in 3d stacked die architectures with varying number of stacked die

Abstract

A handshake mechanism allows die discovery in a stacked die architecture that keeps inputs isolated until the handshake is complete. Power good indications are used as handshake signals between the die. A die keeps inputs isolated from above until a power good indication from the die above indicates presence of the die above. The die keeps inputs isolated from below until the die detects power is good and receives a power good indication from the die and the die below. In an implementation drivers and receivers, apart from configuration bus drivers and receivers are disabled until a fuse distribution done signal indicates that repairs have been completed. Drivers are then enabled and after a delay to ensure signals are driven, receivers are deisolated. A top die in the die stack never sees a power good indication from a die above and therefore keeps inputs from above isolated. That allows the height of the die stack to be unknown at power on.