13.2.2.4 National Semiconductor MICROWIRE Protocol

The National Semiconductor MICROWIRE serial interface is a half-duplex protocol using a master/slave message passing technique. Each serial transmission begins with an 8-bit control word, during which time no incoming data is received. After the control word is sent, the external slave decodes it, and after waiting one serial clock cycle from the end of the control word, responds with the required data, which may be 4 to 16 bits in length.