SBAS430F January 2009 – April 2018 DAC7568 , DAC8168 , DAC8568
PRODUCTION DATA.
Figure 131 shows a serial interface between the DAC7568/DAC8168/DAC8568 and the 68HC11 microcontroller. SCK of the 68HC11 drives the SCLK of the DAC7568, DAC8168, and DAC8568, while the MOSI output drives the serial data line of the DAC. The SYNC signal derives from a port line (PC7), similar to the 8051 diagram.
The 68HC11 should be configured so that its CPOL bit is '0' and its CPHA bit is '1'. This configuration causes data appearing on the MOSI output to be valid on the falling edge of SCK. When data are being transmitted to the DAC, the SYNC line is held low (PC7). Serial data from the 68HC11 are transmitted in 8-bit bytes with only eight falling clock edges occurring in the transmit cycle. (Data are transmitted MSB first.) In order to load data to the DAC7568, DAC8168, and DAC8568, PC7 is left low after the first eight bits are transferred; then, a second and third serial write operation are performed to the DAC. PC7 is taken high at the end of this procedure.