change a bit in a double word

You have to pay attention to byte/word swapping for Siemens formats (Motorola).

In your first code example the way you are doing I believe you are setting the bit M503.0

Dec

Hi!

We had a similar problem, and it was exactly what Ikkezelf said: Siemens' memory allocation's inversion. In our case the confusion was made 'cause WinCC was accessing a 16-bit tag which was an UDT on the PLC side. So the PLC treated the information as bits (which means it didn't invert that data), and the driver in WinCC inverted it 'cause as far as WinCC was concerned that data had been inverted on the PLC side. We solved it by using bytes, since there's no inverting those!

Ikkezelf

...
Mind the double ||
...

Danielle

...
We had a similar problem, and it was exactly what Ikkezelf said: Siemens' memory allocation's inversion. In our case the confusion was made 'cause WinCC was accessing a 16-bit tag which was an UDT on the PLC side. So the PLC treated the information as bits (which means it didn't invert that data), and the driver in WinCC inverted it 'cause as far as WinCC was concerned that data had been inverted on the PLC side. We solved it by using bytes, since there's no inverting those!
...

Dec

Actually overgeo used the right operator "|Bitwise Inclusive OR" in order to set a bit into a DWORD. With the operator “|| Logical - OR” the result is 0 if both operands have 0 values. If either operand has a nonzero value, the result is 1.

Hi ikkezelf,

You can use "||" operator in WinCC C Script with the same results as "|" but this is wrong acording to ANSI-C standards.
It might be right with ANSI-EMENS C standards.

You never know when Siemens will decide to make WinCC C Script fully compliant with ANSI-C, and then your code will be wrong.

Make a C program main.c and compile and execute and see the return code (1):

// main.c
typedef unsigned long DWORD;
DWORD main(void)
{
DWORD val = 0x100;
return val || 0x1000000; // Exit code 1 (0x1).
//return val | 0x1000000; // Exit code 16777472 (0x1000100).
}
// end main.c

Dec