An implantable medical device communication system communicates information between an implantable medical device and at least one slave device by way of a two-wire bus. Slave devices may include remote sensors and other implantable medical devices. The implantable medical device includes a communication unit to combine data and power for transmission over the two wire bus. The transmitted signal is selectively changeable between a first and second voltage. The slave device includes a recovery unit to recover data and power from the received signal. An extendable command set includes long commands to set up the system and shorter commands to conserve power. Selectively addressable multicast commands, and shortened quick trigger commands conserve power by lowering system current and increasing data throughput.