Was hast Du schon in den Subroutinen stehen, bzw. was darf darin vorkommen bis der Fehler mit dem IF auftritt ?
..schon fast nicht‘s mehr, habe schon fast alles wieder rausgestrichen

Nur noch ein minimum ist jetzt drinnen
Code:
Config Twislave = 64 , Btr = 5 , Bitrate = 100000      
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.
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'the following labels are called from the library
Twi_stop_rstart_received:
 ' Print "Master sent stop or repeated start"
Return


Twi_addressed_goread:
  'Print "We were addressed and master will send data"
Return


Twi_addressed_gowrite:
  'Print "We were addressed and master will read data"
Return

'this label is called when the master sends data and the slave has received the byte
'the variable TWI holds the received value
Twi_gotdata:
   'Print "Empf: " ; Twi

    Twi_daten = Twi                                         ' neue Daten merken
    Neuesbyte = 1                                           ' merken das ein neues Byte da ist


Return

'this label is called when the master receives data and needs a byte
'the variable twi_btr is a byte variable that holds the index of the needed byte
'so when sending multiple bytes from an array, twi_btr can be used for the index

Twi_master_needs_byte:

             Select Case Twi_btr
                Case 1 : Twi = Low(liter)
                Case 2 : Twi = High(liter)
                Case 3 : Twi = Low(menge)
                Case 4 : Twi = High(menge)
                Case 5 : Twi = Liter_soll

              End Select

    'Print "Sende = " ; Twi

Return

'when the mast has all bytes received this label will be called
Twi_master_need_nomore_byte:
  'Print "Master does not need anymore bytes"
Return

kann mir mal bitte einer betätigen das die
i2c_TWI-slave.LBX - - > 1.11.7.5 30.June2004 die
"Neuste" ist ?
oder wo bekommt man für die zusätzlich erworbenen Lib‘s die Updats?

Werde es dann mal andersrum testen, und die
if then's in das Beispielprogramm von MCS einfugen