7.5.3.1 Writing

To write to a single DAC register

1. 1. Send a START condition on the bus.
2. Send the device address and read/write bit = LOW. The BUF20800-Q1 will acknowledge this byte.
3. Send a DAC address byte. Bits D7−D5 must be set to 0. Bits D4−D0 are the DAC address. Only DAC addresses 00000 to 10011 are valid and will be acknowledged. Table 3 shows the DAC addresses.
4. Send two bytes of data for the specified DAC register. Begin by sending the most significant byte first (bits D15−D8, of which only bits D9 and D8 are used, and bits D15−D14 must not be 01), followed by the least significant byte (bits D7−D0). The register is updated after receiving the second byte.
5. Send a STOP condition on the bus

The BUF20800-Q1 will acknowledge each data byte. If the master terminates communication early by sending a STOP or START condition on the bus, the specified register will not be updated. Updating the DAC register is not the same as updating the DAC output voltage. See the Output Latch section.

The process of updating multiple DAC registers begins the same as when updating a single register. However, instead of sending a STOP condition after writing the addressed register, the master continues to send data for the next register. The BUF20800-Q1 automatically and sequentially steps through subsequent registers as additional data is sent. The process continues until all desired registers have been updated or a STOP condition is sent.

To write to multiple DAC registers:

1. 1. Send a START condition on the bus.
2. Send the device address and read/write bit = LOW. The BUF20800-Q1 will acknowledge this byte.
3. Send either the DAC_1 address byte to start at the first DAC, or send the address byte for whichever DAC will be the first in the sequence of DACs to be updated. The BUF20800-Q1 will begin with this DAC and step through subsequent DACs in sequential order.
4. Send the bytes of data; begin by sending the most significant byte (bits D15−D8, of which only bits D9 and D8 have meaning), followed by the least significant byte (bits D7−D0). The first two bytes are for the DAC addressed in step 3 above. Its register is automatically updated after receiving the second byte. The next two bytes are for the following DAC. That DAC register is updated after receiving the fourth byte. This process continues until the registers of all following DACs have been updated.
5. Send a STOP condition on the bus.

The BUF20800-Q1 will acknowledge each byte. To terminate communication, send a STOP or START condition on the bus. Only DAC registers that have received both bytes of data will be updated.