Interfacing a DS1390/DS1391 RT

The DS1390 Real-Time Clock (RTC) may be interfaced with a microcontroller (μC) or Digital Signal Processing (DSP) unit using a SPI interface. This app note shows how to connect a DS1390 to a Motorola DSP that has a built-in SPI interface module. This circuit uses the Motorola DSP56F800DEMO Demonstration Board and CodeWarrior IDE. Using the Example Software The example software was developed by starting with a blank project. Follow the instructions in the Motorola Kit Installation Guide (Tutorial: Creating a CodeWarrior Project) for details. Add the code included in this application note in main.c. Operation
The program uses a GPIO port to control CS on the DS1390. The software initializes the SPI controller module and the DSP writes the time and date to the DS1390. The software then loops reading the time and date. The DS1390 and DS1391 support SPI modes 1and 3.