tvey
Lifetime Supporting Member
Hi folks,
I worked on a project recently using Siemens WinCC Flexible and encountered a somewhat annoying issue with alarming and alarm 'trigger bits'.
WinCC Flexible was, apparently, at one time called 'ProTool'. The ProTool package used a different byte organization (look up 'little endian vs. big endian').
I'm using S7-200 series addresses below.
In one scheme, a word looks like this:
Byte2 Byte1
VB907 VB906
In the other scheme, a word looks like this:
Byte1 Byte2
VB906 VB907
The S7-200 series PLC uses the first scheme. WinCC Flexible ALSO uses the first scheme, EXCEPT when it comes to looking up text for alarm trigger bits.
Let's say I have an alarm assigned in the PLC to bit V906.0 - "Y-Axis Failed to Home'.
To configure an alarm in WinCC Flexible, you must create a tag to serve as the 'trigger tag', then assign alarm text for each 'trigger bit' within the trigger tag.
Logically, I expected to assign the trigger tag to VW906, and then assign the appropriate alarm text to 'trigger bit' 0.
HOWEVER, because of the (undocumented, as far as I can tell) endian issue above, this setup won't work! WinCC Flexible is apparently smart enough to know that bit V906.0 is set, but falls down when it does the lookup for the alarm text.
To make the alarm text show up properly, you must account for the swapped byte order - so instead of assigning the alarm text to trigger bit 0 (as would match the actual alarm bit in the PLC), you must assign the alarm text to trigger bit 8 (and so on for the low byte).
Siemens tech support enlightened me to this issue yesterday. I walked our client through the 'fix' but haven't yet heard back whether or not the problem is actually solved.
Has anyone else encountered an issue like this (or similar) with WinCC Flexible or other HMI package?
-Trevor
Here is an example of 'trigger tag' and 'trigger bit' assignments:
'trigger tag' assignment
'trigger bit' assignment
I worked on a project recently using Siemens WinCC Flexible and encountered a somewhat annoying issue with alarming and alarm 'trigger bits'.
WinCC Flexible was, apparently, at one time called 'ProTool'. The ProTool package used a different byte organization (look up 'little endian vs. big endian').
I'm using S7-200 series addresses below.
In one scheme, a word looks like this:
Byte2 Byte1
VB907 VB906
In the other scheme, a word looks like this:
Byte1 Byte2
VB906 VB907
The S7-200 series PLC uses the first scheme. WinCC Flexible ALSO uses the first scheme, EXCEPT when it comes to looking up text for alarm trigger bits.
Let's say I have an alarm assigned in the PLC to bit V906.0 - "Y-Axis Failed to Home'.
To configure an alarm in WinCC Flexible, you must create a tag to serve as the 'trigger tag', then assign alarm text for each 'trigger bit' within the trigger tag.
Logically, I expected to assign the trigger tag to VW906, and then assign the appropriate alarm text to 'trigger bit' 0.
HOWEVER, because of the (undocumented, as far as I can tell) endian issue above, this setup won't work! WinCC Flexible is apparently smart enough to know that bit V906.0 is set, but falls down when it does the lookup for the alarm text.
To make the alarm text show up properly, you must account for the swapped byte order - so instead of assigning the alarm text to trigger bit 0 (as would match the actual alarm bit in the PLC), you must assign the alarm text to trigger bit 8 (and so on for the low byte).
Siemens tech support enlightened me to this issue yesterday. I walked our client through the 'fix' but haven't yet heard back whether or not the problem is actually solved.
Has anyone else encountered an issue like this (or similar) with WinCC Flexible or other HMI package?
-Trevor
Here is an example of 'trigger tag' and 'trigger bit' assignments:
'trigger tag' assignment
'trigger bit' assignment