Abstract: A writing current circuit (42) supplies a controlled electrical current to a laser diode (34) for recording data swiftly onto a DVD (16). A plurality of current sources (62) in the writing current circuit (42) supply electrical current directly to the laser diode (34). Each current source (62) respectively receives a single output signal from a current control register (52) included in the writing current circuit (42) which activates or deactivates the current source (62) for supplying a particular quantity of current to the laser diode (34). In one aspect, a pair of current reference signals received by the current source (62) control electrical current supply to the diode (34). Incorporated into these controlling reference signals is a simulation of electrical characteristics of the diode (34). In another aspect, each current source (62) responds to a logical inverse of the output signal from the current control register (52) for controlling overshoot in voltage applied across the diode (34).

Abstract: A digital logic simulation/emulation system (20) operates in an engaged operating mode in which a digital-logic simulation process (22) transmits stimulation-control data to a hardware pod (32) for controlling stimulation of a digital logic circuit. In response to the stimulation-control data, the hardware pod (32) performs a stimulation-response cycle, and then sends response data from the digital logic circuit to the simulation process (22). The simulation process (22) and the hardware pod (32) may also operate in a disengaged operating mode in which each operates independently of the other without exchanging stimulation-control data or response data. Operation of the system (20) in the disengaged mode commences if a disengagement event occurs in the hardware pod (32). Operation of the system (20) in the disengaged mode terminates if the simulation process (22) sends stimulation-control data to the hardware pod (32), or if the hardware pod (32) sends response data to the simulation process (22).