reading from an S7-1200 - DB100.10 (real value)

[stevennoppe]

In my PLC I have a DB100 from which I want to read from.

I have 4 variables in the DB100 : DB100.0 = real DB100.4 = real DB100.8 = int DB100.10 = real

I can read and show the first 3 variables with my code, but when I try to read the last variable, I get an "address out of range" error. But I cannot seem to find out why I cannot read that last variable.

This is my code :

# function for reading the data easier
def ReadMemory(plc, db, byte, bit, datatype):
  result = plc.read_area(areas['DB'],db,byte,datatype)
  if datatype==S7WLBit:
    return get_bool(result,0,1)
  elif datatype==S7WLByte or datatype==S7WLWord:
    return get_int(result,0)
  elif datatype==S7WLReal:
    return get_real(result,0)
  elif datatype==S7WLDWord:
    return get_dword(result,0)
  else:
    return None

    #read DB100.0
    Machine_speed = ReadMemory(plc_slakbewaking,100,0,0,S7WLReal)

    #read DB100.4
    Roll_length = ReadMemory(plc_slakbewaking,100,4,0,S7WLReal)

    #read DB100.8
    Knife_3_level = ReadMemory(plc_slakbewaking,100,8,0,S7WLWord)

    #read DB100.10
    Knife_3_laser_value = ReadMemory(plc_slakbewaking,100,10,0,S7WLReal)

What's happening? :(

• Optimized Block access is of for this DB
• Put/get communication is on
• access level is set as "full"

[lautarodapin]

# function for reading the data easier
def ReadMemory(plc, db, byte, bit, datatype):
  result = plc.read_area(areas['DB'],db,byte, byte + datatype) # <---- HERE if is bool it should be +1 in case of 2bytes +2 in case of 4bytes +4
  if datatype==S7WLBit:
    return get_bool(result,0,1)
  elif datatype==S7WLByte or datatype==S7WLWord:
    return get_int(result,0)
  elif datatype==S7WLReal:
    return get_real(result,0)
  elif datatype==S7WLDWord:
    return get_dword(result,0)
  else:
    return None

    #read DB100.0
    Machine_speed = ReadMemory(plc_slakbewaking,100,0,0,S7WLReal)

    #read DB100.4
    Roll_length = ReadMemory(plc_slakbewaking,100,4,0,S7WLReal)

    #read DB100.8
    Knife_3_level = ReadMemory(plc_slakbewaking,100,8,0,S7WLWord)

    #read DB100.10
    Knife_3_laser_value = ReadMemory(plc_slakbewaking,100,10,0,S7WLReal)

[stevennoppe]

Hello, Thx for the reply. I will try this Monday. But I wonder why does it work for the first 2 real values and not for that last one?

[lautarodapin]

I notice an error of my part. If you are using the module types from snap7 (Ex: S7WLReal) those values are hexa, that is why it worked for some of the values but not for all of them. you could use the ADict wordlen_to_ctypes to check for the length

read_area(AreaType, number, 0, end + offset) 

[gijzelaerr]

i guess this question has been answered.