Page 133 - Making PIC Microcontroller Instruments and Controllers

SOCKET U6-HEAL.TIME CLOCKS I23

1N4148

l
1 N 4 1 4 8 39
3 3a
3T
5 36
6 35
34
33
32
31
1 1 30
1 2 29
1 3 2A
U6 c5 27
c3 9qLK t 5 26
1 6
FIST 1 7 25
frl t 9 2 1
DS1302 1 a 23
22
2A
32.764 KHz

FIEAL TIME CLOCK OPTION 3

f!t1ta"l,!ii1,r clock implemenled usins lc Dsl302. (To ihe McU, this c ock lc
like a sel oJ memorv locations.)

Before you can use the NJU6355. the DSI202. or the DS 1302, you have to install a
crystal bctwecn pins 2 and 3 ofthc chip sockct. This has to be a 32.768 kHz crystal.rnd
il is to bc inslallcd ar junpcr J5 nexr 1() the real time clock lC sockct. If you do not h ave
a crystal in place, the program will show the date and other itens on the LCD, bul thc
clock rvill not move forward.
lf you want to have battery backup for the clock, you need to install a battery at
junrper J4 (at the edge of thc board ncxt 10 U I0). Thc pins tbr this jumper are already
on thc board whcn you receivei!. The IC will accept lion 2.0 to 5.5 volts. so threeAA
cclls in scrics can proridc an incxpcnsivc backup powcr sourcc. (Thc powerdrawo by
this lC is 300 nano amps a! 2.0 volls. TwoAA cclls may nol proridc cnough voltage
bccause of the voltagsdrcpacrcss
thein line diode. so I ha! c rccommcndcd thrcc cells. )
The DSl3o2 (in Socket u6l The DS1302 is the successor to the DSl202. Thc
DSl302IC is very simihrexceprfor backup po\\,er capability aDd seven addition.rl bytes
ofscratch pad memory. Sec thc datashcct for morc spccific details.