An 8-pin RTC chip, DS1202 provides an accurate digital clock for real-time applications. Example circuit shown above requires 3-pin for interfacing with 8051 chip, P1.3, P1.4 and P1.5. For the DS1202 chip, backup supply, +V requires a signal diode, say 1N914 to switch between normal supply and +3V lithium battery. Newer version DS1302 has an internal switching diode, +3V battery supply can then be connected directly. My friend, Santi Hankla, wrote me the library extension for DS1202, DS1202.ASM. The library extension is used with Micro-C Compiler written in Assembly. To use the extension, you have to add the name and label of the DS1202.ASM in the TINY.LIB. He also provides me the example C program, REALTIME.C, sending real-time clock to terminal every second.
 
 

I have tested above circuit with DS5000, soft-microcontroller 8051 compatible, it works well. But with ATMEL 89C52, 89C55, three 20k resistors should be changed to 40k. Moreover a bypassing capacitor, 0.1uF ceramic should be put at Vcc and GND.

Wichit Sirichote, kswichit@kmitl.ac.th

Last updated, 30 December 2542