Communication to a Message-based device is done using the device communication registers and the WordSerial protocol. The WordSerial protocol is implemented by writing or reading 16 bit words one at a time to/From the Data Low register located on the device. The communication is paced by the bits in the device Response register (Read Ready or Write Ready).
LongwordSerial and Extended LogwordSerial protocols are also supported by some devices. These protocols are similar to the WordSerial protocol. However instead of using 16 bits as a word, 32 and 48 bits are used.