Use the RREG command to read the device register data. Read the register data one register at a time, or read as a block of register data. The starting register address is any register in the map. The RREG opcode consists of two bytes. The first byte specifies the starting register address: 001r rrrr: where r rrrr is the starting register address. The second opcode byte is the number of registers to read (minus 1): 000n nnnn: where n nnnn is the number of registers to read minus 1.
After the read command is sent, the ADC responds with one or more register data bytes, most significant bit first. If the byte count exceeds the last register address, the ADC begins to output zero data (the address pointer does not wrap). During the register read operation, if ADC1 data are ready, the conversion data are not loaded to the output shift register to avoid data contention. However, the conversion data can be retrieved later by the RDATA1 command. After the register read command has been started, further commands are disabled until one of the following conditions:
1) The read operation is completed.
2) The read operation is terminated by taking CS high.
3) The read operation is terminated by a serial interface autoreset.
4) The ADC is reset by toggling the RESET/PWDN pin.
Figure 9-56 depicts a two-register read operation example. As shown, the opcodes required to read data from two registers starting at register MODE2 (address = 05h) are: OPCODE 1 = 25h and OPCODE 2 = 01h. Keep the DIN input low after the two opcode bytes are sent.