Sigma-7Siec

One common cause of the CPU load being higher than expected is caused by using a custom Function Block that uses a large structure connected as a VAR_INPUT instead of a VAR_IN_OUT.

When a variable is declared as a VAR_INPUT, the MPiec Controller copies the entire contents of the structure into the Function Block every scan. Other programming languages refer to this technique as “Passing by Value.”  In this situation, the Function Block does not have the ability to alter the contents of the original data. When declaring a variable as VAR_IN_OUT, the MPiec Controller passes a pointer to the original location of the variable rather than a copy of the data. Other programming languages refer to this technique as “Passing by Reference.” The pointer is an internal 32 bit value, which is significantly more efficient than copying the entire contents every scan. This method also gives the Function Block the ability to alter the contents of the structure variable.

To show this example in practice, the attached document shows two scenarios. The first scenario scans a Function Block with a large structure as a VAR_INPUT and results in a high CPU load. The other scenario shows the same structure as a VAR_IN_OUT and has no impact on the CPU load.

The large structure is an array of an array creating 500,000 LREAL’s. There is nothing else in the program, the custom Function Blocks have no code.

If the Vipa Ethernet coupler was previously configured and then modules are added or changed, you must perform an online save through its web page before they will function correctly.  If the new configuration is not saved, the Vipa Ethernet coupler will flash the SF and MS red LED’s when the controller connects.  The I/O status variable in the MotionWorks IEC project will show a status of 0x1000 (connected) or 0x320 (deleted configuration) but the I/O will not update.

To save the configuration on the Vipa Ethernet coupler:

Open the Vipa web page by typing the IP address into the browser’s address bar.

Note:  Disconnect or stop any MPiec controller Ethernet connection to the Vipa bus coupler.

Navigate to the Configuration tab and press the Save button.

After saving the configuration, the Vipa Ethernet coupler must be powered down for at least 20 seconds, and then powered back up.  If the power is short cycled, the Vipa Ethernet coupler will not power up.

See attached document for a screen shot of the web page’s Configuration tab

Invalid Segment Type Error 16#315 may result if configuration instances of the adapter (SigmaLogic EIP Node) are swapped.

Valid configuration instances of the adapter should be as follows.

Input :
Assembly Instance  : 102 ;
Size : 64 (32-bit);

Output :
Assembly Instance  : 112 ;
Size : 64 (32-bit)

Configuration :
Assembly Instance  : 1 ;
Size : 1(8-bit)

See attached document

There are two cases when this may occur. If the library cannot be found on the PC or if the library is marked as open.

See attached document for instructions.