Autonomous selection of output buffer characteristics as determined by

Abstract

A mechanism determines at least an approximation of output load coupled to a programmable output buffer, and then programs the buffer to source/sink an amount of output current appropriate to the load to be driven. The mechanism includes a load recognition unit, an optional signal conditioner, and a reconfiguration logic module. In interface-governed applications, the load recognition unit senses an interface bit (AT Attachment interface), or causes the output buffer to act as a master unit that polls the interface connection to determine the number of attached loads (SCSI interface). The recognition unit then outputs a signal that may be conditioned before being input to a reconfiguration logic module that outputs appropriate control signals that program the buffer. Alternatively, the load recognition unit may measure the shunt capacitance associated with the load by using a reference current source and an analog/digital converter. The resultant voltage developed across the shunt capacitance provides a measure of the load impedance, which is used by the reconfiguration logic module to output control signals appropriately configuring the output buffer. Preferably the output buffer includes a plurality of individually-enableable unit buffers. The reconfiguration logic module can enable only such unit buffers whose current handling contributions are necessary to drive the approximated or measured load to be driven.