IF NOT AND question

2020-02-27T13:48:02.039000Z

FUNCTION write_value_bool : BOOL
VAR_INPUT
   PLC         : POINTER TO ModbusSlaveComPort;
END_VAR
IF PLC^.xInitDone AND NOT PLC^.xError THEN
        write_value_bool:= TRUE;
ELSE
        write_value_bool:= FALSE;
END_IF

One should avoid the above IF THEN statements. A better solution could be;

write_value_bool := PLC^.xInitDone AND NOT PLC^.xError;

Which (better) readable is something like;

FUNCTION xWrtRdy : BOOL
VAR_INPUT
   pMbCom : POINTER TO ModbusSlaveComPort;
END_VAR
xWrtRdy := pMbCom^.xInitDone AND NOT pMbCom^.xError

Now your code is more atomic in nature and "what's in a name". Also, this function can very easily be transformed to a method of some FB.

IF NOT AND question

2020-02-27T13:48:01.973000Z

PhilipLykov hat geschrieben:
… xInitDone to become FALSE or xError TRUE...

This does not match written code. Written code says you have to wait xInitDone to TRUE AND xError to FALSE.

IF NOT AND question

2020-02-27T13:48:01.859000Z

dFx hat geschrieben:
and if you try :

IF PLC^.xInitDone AND NOT (PLC^.xError) THEN

Unfortunately it doesn't help. Only nested IFs works fine.
For those who want to reproduce it:

FUNCTION write_value_bool : BOOL
VAR_INPUT
   PLC         : POINTER TO ModbusSlaveComPort;
END_VAR
IF PLC^.xInitDone AND NOT PLC^.xError THEN
        write_value_bool:= TRUE;
ELSE
        write_value_bool:= FALSE;
END_IF

And yes, you have to wait for xInitDone to become FALSE or xError TRUE. For this purpose you can do xReset:= TRUE (at ModbusSlaveComPort) for one cycle.

IF NOT AND question

2020-02-27T13:48:01.769000Z

Sorry I misunderstood you...

Can you provide a small example application to easyly reproduce?

Best regards,
Marcel

IF NOT AND question

2020-02-27T13:48:01.653000Z

and if you try :

IF PLC^.xInitDone AND NOT (PLC^.xError) THEN

IF NOT AND question

2020-02-27T13:48:01.592000Z

m.prestel hat geschrieben:
Hello Sir,
ST checks for all the conditions and does not stop early.
AND_THEN does what you describe with nested ifs.
Best regards,
Marcel

Sorry Marcel,
I didn't understood your idea.

IF NOT AND question

2020-02-27T13:48:01.525000Z

dFx hat geschrieben:
What is the result if you replace dereferenced pointers by only boolean variables ?

It works as expected.

IF NOT AND question

2020-02-27T13:48:01.429000Z

Hello Sir,

ST checks for all the conditions and does not stop early.

AND_THEN does what you describe with nested ifs.

Best regards,
Marcel

IF NOT AND question

2020-02-27T13:48:01.339000Z

What is the result if you replace dereferenced pointers by only boolean variables ?

IF NOT AND question

2020-02-27T13:48:01.203000Z

Could you please explain why the following statement is always FALSE:

IF PLC^.xInitDone AND NOT PLC^.xError THEN

It runs on RaspberryPi with the latest Codesys Runtime.
PLC is a pointer to ModbusSlaveComPort.
The xInitDone is TRUE, xError is FALSE.

If I rewrite the code in such way it works as expected:

IF PLC^.xInitDone THEN
   IF NOT PLC^.xError THEN

Recent posts to IF NOT AND question

IF NOT AND question

IF NOT AND question

IF NOT AND question

IF NOT AND question

IF NOT AND question

IF NOT AND question

IF NOT AND question

IF NOT AND question

IF NOT AND question

IF NOT AND question