Abstract: This application note describes how to interface a DS1305 real-time clock with the DS2250, an 8051-type microcontroller. Example code, written in C, shows basic interface routines. DS1305 Pin Assignment Description This application note demonstrates how to interface a DS1305 Serial Alarm Real-Time Clock (RTC) to an 8051-type microcontroller. Example code shows basic interface routines. The microcontroller used in this example is the DS2250 Soft Microcontroller Module, and the software is written in C. The program demonstrates setting and reading the time and date, writing and reading the RAM, and setting and reading an alarm. Operation The interface program uses three general-purpose port pins (GPIOs) on the microcontroller and the 3-wire interface to communicate with the DS1305 real-time clock. An additional port pin is used to monitor the INT0 interrupt output on the DS1305. The software is shown in Figure 1. A schematic of the circuit is shown in Figure 2. Download zip file Figure 1. Interface Program Listing For Larger Image Figure 2. Schematic of DS1305. We Want Your Feedback! Automatic Updates Would you like to be automatically notified when new application notes are published in your areas of interest? Sign up for EE-Mail™. More Information   APP 3510: May 24, 2005 DS1305 Serial Alarm Real-Time Clock Full Data Sheet (PDF, 496kB) Free Samples DS1306 Serial Alarm Real-Time Clock Full Data Sheet (PDF, 560kB) Free Samples DS1392 Low-Voltage SPI/3-Wire RTCs with Trickle Charger Full Data Sheet (PDF, 388kB) Free Samples DS1393 Low-Voltage SPI/3-Wire RTCs with Trickle Charger Full Data Sheet (PDF, 388kB) Free Samples DS2250 Soft Microcontroller Module Full Data Sheet (PDF, 456kB)   Download, PDF Format (34kB)  AN3510, AN 3510, APP3510, Appnote3510, Appnote 3510