JAJS398F January 2009 – April 2018 DAC7568 , DAC8168 , DAC8568
PRODUCTION DATA.
Figure 125 shows a serial interface between the DAC7568, DAC8168, and DAC8568 and a typical 8051-type microcontroller. The setup for the interface is as follows: TXD of the 8051 drives SCLK of the DAC7568, DAC8168, or DAC8568, while RXD drives the serial data line of the device. The SYNC signal is derived from a bit-programmable pin on the port of the 8051; in this case, port line P3.3 is used. When data are to be transmitted to the DAC7568, DAC8168, and DAC8568, P3.3 is taken low. The 8051 transmits data in 8-bit bytes; thus, only eight falling clock edges occur in the transmit cycle. To load data to the DAC, P3.3 is left low after the first eight bits are transmitted; then, a second write cycle is initiated to transmit the second byte of data. P3.3 is taken high following the completion of the third write cycle. The 8051 outputs the serial data in a format that has the LSB first. The DAC7568, DAC8168, and DAC8568 require the data with the MSB as the first bit received. Therefore, the 8051 transmit routine must take this requirement into account, and mirror the data as needed.