Digital integrated circuits.

摘要

A digital integrated circuit is described in which the internal registers are organised into a number of serial shift paths (12) to facilitate testing. Each path has a number of modes: USER, HOLD, SHIFT and SELF-TEST modes. These modes are controlled by shifting a control function into a control shift register (13). When the shifting of the control shift register stops, a command is automatically loaded from the control shift register (or another source) into a command register (60), which controls the serial shift paths (12). The provision of a separate command register allows a new control function to be shifted into the control shift register while a preceding command is still active in the command register.