Problem with DS1620

[user01]

My 68HC11 project is complete, but when show the temperature on the LCD it always show 28.5 oC, or in BCD – 00111001. I don’t know why. I read the code couple of times to make sure that I didn’t make something wrong. Can somebody help me.

This code I took from here: EMICROS - Talking to a Dallas DS1620 and modify it little because it was showing 0 oC

This is fragments of the code:


RSTTEMP equ %00100000
I_O equ %00001000
SCLK equ %00010000




ReadTemperature:
ldx #REGBLK
bset DDRD,x %00111000
bclr PortD,x SCLK
bset PortD,x RSTTEMP
ldaa #$AA

ldab #8
ZS:
bclr PortD,x I_O
lsra
bcc NS
bset PortD,x I_O
NS:
bset PortD,x SCLK
nop
nop
nop
bclr PortD,x SCLK
decb
bne ZS

clr TempLSB
clr TempMSB
bclr DDRD,x I_O
ldab #8
JJ:
nop
nop
nop
bset PortD,x SCLK
clc
brclr PortD,x I_O HJ
sec
HJ:
ror TempLSB
bclr PortD,x SCLK
decb
bne JJ

bset PortD,x SCLK
brclr PortD,x I_O AD
ldaa #1
staa TempMSB

AD:
bclr PortD,x SCLK
bset DDRD,x I_O
bclr PortD,x RSTTEMP
ldab TempLSB
rts




BCD2STR:
psha
anda #$0F
oraa #$30
staa 1,x
pula
asra
asra
asra
asra
anda #$0F
oraa #$30
staa 0,x
rts




ldaa Str2+1
cmpa LastSecond
beq NoNewTemp
staa LastSecond
jsr ReadTemperature
lsrb
bcc Set00
ldaa #'5'
bra Set05
Set00:
ldaa #'0'
Set05:
staa Str2+12

clra
tba
ldx #Str2+9
jsr BCD2STR
clrb
ldab TempMSB
cmpb #$1
bne NoNewTemp
ldaa #'-'
staa Str2+8

 

[user01]

I put this code in the initialization:

ldx #REGBLK
bset DDRD,x %00111000
bclr PortD,x SCLK
bset PortD,x RSTTEMP
ldaa #$EE

ldab #8
ZS1:
bclr PortD,x I_O
lsra
bcc NS1
bset PortD,x I_O
NS:
bset PortD,x SCLK
nop
nop
nop
bclr PortD,x SCLK
decb
bne ZS1


When I done this I begin to get different readings such as 3=, 2> and so on.

So I put this code for the convertion from BCD to degrees, showing on LCD:

clra
ldx #10
idiv
orab #$30
stab str2+10
xgdx
ldx #10
idiv
orab #$30
stab str2+9


When I put it I begin to get from 40oC to 65-70oC, but without any marks or unknown symbols.

I'm surprised of this reading, because the temperature on the corpus of the device is not more than 25-27oC, even colder.

Is there an error in the code for the conversion?
Can somebody tell me better method?