| 摘要 |
A chip (10) consists of a plurality of subsystems (20-26), with the state machines in each subsystem being coupled to a status bus (36), and status selection and multiplexing means selecting any of the subsystems so that its state machines can be monitored (eg for design fault detection) via a set of state monitor pins. The selection means preferably use existing control and data paths of the system, with the system in an off-line state. The status bus can conveniently be 6 data bits plus a clock bit, so that the clock of a selected subsystem is provided along with its state machine states. The status bus can optionally be expanded to allow the state machines of a selected subsystem to be driven to correct a fault, either via an external circuit or by means of on-chip programmable circuitry in the status subsystem (35). Alternatively, a subsystem can be permanently selected and its state machine states used to control an external circuit (71) added to fix the fault by modifying the interfacing functionality with the surrounding chips. |
