9.5.3.12 WREG

Use the WREG command to write the device register data. The register data are written one register at a time or as a block of register data. The starting register address is any register in the register map.

The WREG command consists of two bytes. The first byte specifies the starting register address: 010r rrrr, where r rrrr is the starting register address The second command byte is the number of registers to write (minus 1): 000n nnnn, where n nnnn is the number of registers to write minus 1. The following byte (or bytes) is the register data, most significant bit (MSB) first. If the byte count exceeds the last register address, the ADC ignores the data. After the register write command has started, further commands are blocked until one of the following conditions are met:

• The write operation is completed
• The write operation is terminated by taking CS high
• The write operation is terminated by a serial interface timeout
• The ADC is reset by toggling the RESET pin

Figure 75 shows a two-register write operation example. As shown, the required commands to write data to two registers starting at register REF (address = 05h) are: command byte 1 = 45h and command byte 2 = 01h.

1. CS can be set high or kept low between commands. If kept low, the command must be completed.

Figure 75. Write Register Sequence

Writing new data to certain configuration registers resets the digital filter. Resetting the digital filter clears the output shift register and if a conversion is in progress, a new conversion starts. Writing to the following registers triggers a new conversion:

• Channel configuration register (02h)
• Gain setting register (03h)
• Data rate register (04h)
• Reference control register (05h), bits [5:0]
• Excitation current register 1 (06h), bits [3:0]
• Excitation current register 2 (07h)
• System control register (09h), bits [7:5]

When the device is configured with WREG, the first data ready indication occurs after the new conversion completes with the configuration settings. The previous conversion data are cleared at restart; therefore read the previous data before the register write operation. Again, a WREG to these registers only starts a new conversion if a conversion is in progress. If the device is in standby mode, the device sets the configuration according to the WREG data, but does not start a conversion until the START/SYNC pin is taken high or a START command is issued.