Math for dunce...

I have three value : 25 ; 25.23 ; 26.02
I must do this : If 26.02 - (25/100) > 25.23 then do something...
Since the numbers are not integers, my results are wrongs. Please, a little help. Thanks in advance.

Just multiply everything by 100.
Then it becomes ...

If (2602 - 25) > 2523 then do something...
<br>

Thank You, Mr.Darrel !
I have already do this, but...Maybe it's another mistake..So, I put the code.
I read the temperature :

Code:

---

OWOut DQ, 1, [$CC, $44]
 OWOut DQ, 1, [$CC, $BE]
 OWIn DQ, 2, [temperature.byte0, temperature.byte1]       
                SignBit = 0
                if  temperature.15 then 
                    temperature  = ~ temperature + 1
                    SignBit = 1
                endif 
               
Dummy = 625 * Temperature
TempC = DIV32 10
TempC = (Temperature & $7FF) >> 4
Float = ((Temperature.Lowbyte & $0F ) * 25 )>>2
Temperature=TempC*100 + Float       
        If SignBit then
                  V= 10000 - Temperature          ' 25'C=12500  0'C=10000  -10'C=9000
                  SignBit = 0
            else
                  V= 10000 + Temperature
        EndIf
 
        If V >= 10000 then                    ' Above 0 C.     
                  Temperature=V-10000                 
            else                                 
                  Temperature=10000-V              ' Below 0 C.
        EndIf
 
 GoSub SelectSign                            ' +/blank/- Sign

---

Code:

---

SelectSign:
 If v = 10000 then                              ' Temperature = 0 C.
          Sign=" "                                      ' No sign
    Else
                  If v < 10000 then            ' <> 0
                          Sign="-"                        ' Temperature below 0 C.       
                      Else
                          Sign="+"                        ' Temperature above 0 C.
                  EndIf
 EndIf
Return

---

At the beginning I set the hysterezis for thermostat :

Code:

---

If Mode=1 then                                ' Set Hysteresis 
                LcdReg  =  %10000000 + 12 ' cursor  X
                call    PrintCtrlLcd
                LcdReg  =  %01000010      ' cursor  Y
                call    PrintCtrlLcd         
                Char = 21
                call    PrintChar
                Char = 19
                call    PrintChar 
                Char = 20
                call    PrintChar 
                Char = 15
                call    PrintChar 
  Gosub DTemp                                  ' Display Hysteresis
  If (PORTB.1=0) Or (PORTB.2=0) then            ' Up or down button pushed 

  If PORTB.2=0 then                            ' Down button
            if hyst > 5 then hyst=hyst-5
            If Hyst < 5  then Hyst=5
            Gosub Debounce
  EndIf
  If PORTB.1=0 then                            ' Up button
            hyst=hyst+5
            If Hyst > 50 then Hyst=50
            Gosub Debounce
  EndIf
  Gosub DTemp                            ' Display Hysteresis                       
  EndIf
 EndIf
.....
DTemp :
        LcdReg  =  %10100000 + 14              ' cursor  X 
        call    PrintCtrlLcd
        LcdReg  =  %01000100                  ' cursor  Y
        call    PrintCtrlLcd       
 
        Char = (hyst dig 2) + 2           
        call    PrintChar
        Char = 14                     
        call    PrintChar
        Char = (hyst dig 1) + 2         
        call    PrintChar
        Char = (hyst DIG 0) + 2     
        Call    PrintChar
Return

---

and I try to do this :

Code:

---

check:
 if temperature > (tref + hyst) then
    tref=temperature
                duratavar=(temperature-tref)/hyst
                duratavar=duratavar*durata
        if tipsun=2 then
                sound PORTB.6, [varsnd, duratavar]
                else
                sound PORTB.6, [varsnd, 20]                         
        endIf
 endif

 if temperature < (tref - hyst) then
    tref=temperature
                duratavar=(tref-temperature)/hyst
                duratavar=duratavar*durata
        if tipsun=2 then
                sound PORTB.6, [varsnd2, duratavar]
            else
              sound portb.6, [varsnd2, 10]
        endif
 endif
Return

---

Everything works great, but this "if temperature > (tref + hyst) then" return wrong results.
Note : hyst, temperature, tref are var Word.
Hysterezis must be max 0.50 'C, with step of 0.05 'C. On display works fine, but inside the code I think I made mistake...Thank You !

Not really sure what all is going on in your program fratello.
So let me just show what I would do.

First ... It takes 750mS from the time you start a conversion till you can read the results.
You can just put a pause after the Convert command [$CC, $44], to wait till it's done.
Or you can Poll the DS18B20's busy bit.

Once you have the reading from the DS18B20, it can be converted like this...

Code:

---

    Sign = TempC.15
    TempC = ABS(TempC)
    TempC = ((TempC >> 4)*100) + ((TempC & $F)*100 >> 4)
    IF Sign THEN TempC = -TempC

---

That gives you a Signed Word with 2 decimal places.
25.00 °C would have the value 2500.
-10.00 °C would be -1000.
It will work with the full temperature range of the sensor -55°C to +125°C.

You can display it on an LCD with this ...

Code:

---

DisplayTemp:
    IF TempC.15 THEN LCDOUT "-"
    LCDOUT DEC ABS TempC/100,".", DEC2 ABS TempC,13,10
RETURN

---

To compare the Temp with your hysteresis range, you just subtract the values.
If the value being subtracted is larger than the other one, the result will be negative.
So, just testing for the sign bit tells you if it's above or below the setpoints.

Code:

---

Compare:
    Diff = (tref + Hyst) - TempC
    Over = Diff.15

    Diff = TempC - (tref - Hyst)
    Under = Diff.15
RETURN

---

Over and Under are BIT vars, so you can test them later in the program to activate alarms or whatever.

Keep in mind that with 12-bit resolution, each step of the DS18B20's reading is 0.0625°C.
So incrementing the hyst. 0.05°C won't always give the expected Hyst. range.
It'll be close, but not perfect.

Test program attached.

As always, Mr.Darrel it's one fine Gentleman. Thank You ! I will test and I will post the results !

It's OK, of course !
BTW: Just for fun ; I redefine in my source "hyst" as byte (previous = word) and the results are similares !