8.5.1 SPI Communication

The SPI communication uses a standard SPI interface. Physically the digital interface pins are nCS (Chip Select Not), SDI (Slave Data In), SDO (Slave Data Out) and SCLK (SPI Clock). Each SPI transaction is a 32 bit word containing a command byte followed by two address bytes and length bytes. The data shifted out on the SDO pin for the transaction always starts with the Global Status Register (byte). This register provides the high level status information about the device status. The two data bytes which are the ‘response’ to the command byte are shifted out next. Data bytes shifted out during a write command is content of the registers prior to the new data being written and updating the registers. Data bytes shifted out during a read command are the current content of the registers and the registers will not be updated.

The SPI input data on SDI is sampled on the low to high edge of the SCLK. The SPI output data on SDO is changed on the high to low edge of the SCLK.