Bcd Fomat Help

[financecatalyst]

Convert BCD to decimal... assume variable RTCSeconds holds the seconds in BCD format...

First let's deal with the TENS value (Bits 4,5 and 6)...

DecimalSeconds=RTCSeconds & $70
DecimalSeconds=DecimalSeconds>>4
DecimalSeconds=DecimalSeconds*10

And finally add-in the UNITS value...

DecimalSeconds=DecimalSeconds+(RTCSeconds & $0F)

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To convert Decimal back to BCD, reverse the Process...

RTCSeconds=DecimalSeconds DIG 1
RTCSeconds=RTCSeconds<<4
RTCSeconds=RTCSeconds+(DecimalSeconds DIG 0)

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Incorporate the above into a General Purpose Subroutine and use the same single routine to convert Seconds, Minutes, Hours etc etc.


Melanie

Thanks a lot. I was breaking my head from last few days to learn this. You have really explained it very nicely.

BUT

I am facing slight problem in my simulation (I am using proteus).
My code looks like this when program starts for the first time:

Rtcget		var byte[8]
Rtcsec		var Rtcget[0]
Rtcmin		var Rtcget[1]
Rtchr		var Rtcget[2]
Rtcday		var Rtcget[3]

read 30,check
if check=0 then
	pause 50
	I2CWRITE SDA,SCL,$D0,$00,[$00,$00,$12,$01,$00,$00,$00,$90]
	pause 50
	write 30,1
endif

	I2CREAD SDA,SCL,$D1,$00,[STR Rtcget\8]
		pause 50
		sec=Rtcsec & $70
		sec = sec>>4
		sec=sec*10
		sec=sec +(Rtcsec & $0F)

		minu=Rtcmin & $70
		minu = minu>>4
		minu=minu*10
		minu=minu +(Rtcmin & $0F)

		hrs=Rtchr & $30
		hrs=hrs>>4
		hrs=hrs*10
		hrs=hrs+(Rtchr & $0F)

		if Rtcday=$01 then days=1
		if Rtcday=$02 then days=2
		if Rtcday=$03 then days=3
		if Rtcday=$04 then days=4
		if Rtcday=$05 then days=5
		if Rtcday=$06 then days=6
		if Rtcday=$07 then days=7

& when user changes the time it looks like this

Rtcmin=minu DIG 1
					Rtcmin=Rtcmin<<4
					Rtcmin=Rtcmin+(minu DIG 0)

					Rtchr=hrs DIG 1
					Rtchr=Rtchr<<4
					Rtchr=Rtchr+(hrs DIG 0)

					if days=1 then Rtcday=$01
					if days=2 then Rtcday=$02
					if days=3 then Rtcday=$03
					if days=4 then Rtcday=$04
					if days=5 then Rtcday=$05
					if days=6 then Rtcday=$06
					if days=7 then Rtcday=$07
				I2CWRITE SDA,SCL,$D0,$00,[$00,Rtcmin,Rtchr,Rtcday,$00,$00,$00,$90]
				PAUSE 20

The problem is that during simulation, the frequency of the pulse changes once I set the time (coming from DS1307 - I want 1Hz)
Please point out the problem in my code if any, or is it the simulation software which is not correct (Proteus 6.9)