SMC_AvoidLoop (FB)

FUNCTION_BLOCK SMC_AvoidLoop

The SMC_AvoidLoop function block can be used for path-preprocessing. It will copy a defined path, but cut out the loops contained therein. If an intersection is detected within the original path, the path will be cut at the intersection point, the loop will be removed and the path will be continued with the rest of the curve. Thus, a continuous path free of loops will result.

For a typical application see the description of the SMC_ToolCorr module.

The module passes all SMC_GEOINFO objects found in the input SMC_OUTQUEUE structure. If in one of these objects Bit7 of the variable Intern_Mark is set, the avoid-loop-functionality will be activated. This functionality is able to check, whether there is an intersection point of the current object with any of the subsequent SMC_GEOINFO objects preceding the next SMC_GEOINFO Object, in which Bit6 of the variable Intern_Mark is set. This bit being raised will terminate the avoid-loop-functionality. If no intersections are found, the object will be copied unchanged to the Output SMC_OUTQUEUE . Otherwise the first of the intersecting objects will be cut at the intersection point, the SMC_GEOINFO objects positioned between the intersecting objects will be removed, and the new path will be continued with the second of the two intersecting objects. The SMC_NCDecoder will set the Bits 6 and 7 of Intern_Mark as reaction on the instructions G61/G60.

Note

The efficiency of SMC_AvoidLoop depends on the appropriate size of input SMC_OUTQUEUE. A loop, containing more objects than can be stored in SMC_OUTQUEUE, cannot be detected! On the other hand: For each object an intersection check is executed with all following objects of the queue. If it is a large queue, then it takes long time for completing the check.

InOut:

Scope	Name	Type	Initial	Comment
Input	bExecute	BOOL	FALSE	Execution starts on the rising edge.
	bAbort	BOOL	FALSE	If TRUE, the current processing of this function block is aborted
	bAppend	BOOL	FALSE	As long as this input remains FALSE, DataOutQueue will be cleared at each reset. As long as it remains TRUE, newly incoming data will be written to the end of DataOutQueue.
	poqDataIn	POINTER TO SMC_OUTQUEUE	NULL	This variable points to the SMC_OUTQUEUE structure object, which contains the SMC_GEOINFO objects of the path; typically it points on the output DataOut of the preceding module (e.g. the SMC_NCDecoder ). SMC_OUTQUEUE should be dimensioned in an appropriate size (see nSizeOutQueue) !
	nSizeOutQueue	UDINT	0	This variable contains the size of the data buffer, the list of SMC_GEOINFO structure objects will be written to. This buffer must be able to hold at least five SMC_GEOINFO objects. Otherwise, SMC_NCDecoder will not execute any actions at all. Its size may be predefined, but may be modified later only during a reset. It is recommended to create the buffer as described by the example below. ExampleBuf: Array[ 1..50] of SMC_GeoInfo The appropriate buffer size will then be retrieved by use of the operator sizeof(ExampleBuf).
	pbyBufferOutQueue	POINTER TO ARRAY [0..0] OF SMC_GEOINFO	NULL	This input must point to the first byte of the memory area that is allocated for the SMC_OUTQUEUE structure. This area must be at least as big as defined in nSizeOutQueue. Typically the allocation of the memory buffer is done in the declaration part of the IEC-program by defining an array of SMC_GEOINFO e.g. BUF: ARRAY[1..50] OF SMC_GEOINFO; for a buffer that can store 50 path elements). The value may be predefined, but may be modified later on only during a reset.
Output	bDone	BOOL	FALSE	This variable will be set to TRUE as soon as the input data of ...DataIn has been processed completely. Thereafter the module will not perform any further actions until it will be reset. If input bExecute is FALSE, bDone will be reset to FALSE.
	bBusy	BOOL	FALSE	TRUE, while execution of function block is not finished
	bError	BOOL	FALSE	Signals, that an error has occurred within the function block
	wErrorID	SMC_ERROR	SMC_NO_ERROR	Error identification
	poqDataOut	POINTER TO SMC_OUTQUEUE	NULL	This variable points to a SMC_OUTQUEUE structure, which manages the SMC_GEOINFO objects of the loopless path.
	iStatus	SMC_AL_STATUS	0	This enum variable shows the current state of the module. Possible states: AL_OFF: 0; Avoid-Loop-functionality switched off AL_ON: 1; Avoid-Loop-functionality switched on AL_END: 2; Processing of the objects terminated SMC_AL_STATUS (ENUM)