74Every byte (8 bits) of actual HART data is sent as an asynchronous serial frame with a start bit, parity bit, and stop bit, so that 11 bits’ worth of time are necessary to communicate 8 bits of real data. These “byte frames” are then packaged into larger message units called HART telegrams (similar to Ethernet data frames) which include bits for synchronizing receiving devices, specifying device addresses, specifying the length of the data payload, communicating device status, etc.