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1、Design of the digital Perpetual Calendar based onreal-time clock chipAbstract:This Electronic calendar usesthe AT89S52 microcontroller as the core for the con trol. Time Circuit which is con stituted by Dallass DS12C887A real-time clock chip achieved a time and date display, it in creased fun cti on
2、 ality for the temperature display and the whole point timekeeping. This paper discusses the hardware circuit of the system, prin ciple in detail,a nd gives the flow chart of the software desig n and the major source code. keywords:microcontroller;real-time clock; Temperaturemeasureme nt1 In troduct
3、i onE-cale ndar-bedroom at home,schools,stati ons and more and more exte nsive use of plaza for peoples lives,study,work great convenien ce. Electr onics cale ndar for the past n eed to re-adjust after power-off time and date,a nd time is a big error. Desig ned the system using real-time clock chip
4、(DS12C887A) as a timer parts,the chip comes with an in ternal crystal oscillator,so that effectively guara ntee the accuracy of the time and hang own internal battery power makes the situati on will con ti nue to update the time information . This design uses AT89S52 as the main controller,in order
5、to improve the practicality of the circuit add temperature measureme nt circuit,timekeep ing and alarm fun cti ons.2 System hardware desig nSchematic circuit show n in Figure 2:System architecture diagram2.1 Power Supply CircuitIn order to reduce circuit costs,the system power supply circuit by the
6、tran sformer tran sformer,three-termi nal in tegrated regulator (L7805 circuit 5V, has a simple,reliable, i nexpe nsive and so on.2.2 Host Con trollerHost co ntroller us ing ATMELs latest MCU Products AT89S52. Apart from the sin gle-chip microcomputer has a MCS-51 series sin gle-chip all the ben efi
7、ts of thin gs,also has 8KB of internal in-system programmable FLASH memory,free and low-power brow n-out mode, greatly reduc ing the power circuit .In additi on, also has a watchdog circuit,a reliable job for the circuit provides greater assura nee.2.3 digital tube display circuitShow circuit with a
8、 high bright ness,l ong life,low cost features such as the LED digital tube. Throughout the show circuit by the digital con trol and display LED drive circuit and decod ing circuit. Because of the system to display the contents of more,a total of 16 digital tube, respectively,with eight shows year,m
9、 on th,day,four show time,show that 22 weeks,2 show the temperature. Con troller in order to save resources,betwee n the con troller and displays add a decodi ng circuit 16 so that would have required the line of con trol in to the circuit on ly 4 con trol li nes,a great save system resources. The d
10、ecoder by the decoder con stitute both 3-8.2.4 Real-time clock chipThis desig n uses the Un ited States Dallas compa ny DS12C887A, the chip can automatically gen erate cen tury,year,m on th,day,hour,m inu te,sec on d,such as time in formatio n. Cen tury the use of internal registers with the softwar
11、e will be able to resolve the Mille nn ium, the problem. The chip has its own in ternal battery-ke ng,exter nal brow n-o ut,the in ternal time in formatio n also be able to main tai n for 10 years. Time for a si ngle day record of 12 hours and there is a 24-hour mode. Time TableWays that also has tw
12、o kinds of binary nu mbers,a nd the other with BCD code express. The chip with 128 bytes of internal RAM,one of 11 bytes used to store time in formatio n,4 bytes of memory chips used to con trol in formati on,known as the con trol register,113-byte gen eral-purpose RAM for users to store temporary i
13、n formatio n. In additi on, users can also program the chip to con trol a variety of square-wave output,a nd its in ternal three-way through the software in terrupt shieldi ng.2.5 Butt ons and temperature measureme nts and circuitThe system in order to make the circuit more easy,butt on circuit desi
14、g n on ly three keys, which are set,+,-, three keys to adjust the cale ndar and clock. The system in order to improve the practicality of the circuit,a n in crease of a temperature display. The system temperature measureme nt circuit using Dallass DS1280. The device because of its low price,easy cir
15、cuits,measureme nt precisi on, etc.2.6 audio sig nal gen erator and driver circuitThe circuits fun ctio n is to receive con trol circuit to send to the en tire point of time and tim ing sig nal,accordi ng to system sett ings produce differe nt freque ncies of audio sig nals,amplificati on by the dri
16、ve circuit to drive speakers to voice their opinions in order to realize the whole point timekeep ing and alarm fun cti ons.3 system software desig nProcedures of the system by the main program in terrupt service fun cti on and pose a nu mber of Functions. Mai n fun ctio n and in terrupt the completi on of the in itializatio n fun cti on. Timer in terrupt fun cti on mai n timi ng clock chip to complete sca nning and keypad sca nni
