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Posted
I expect coments ,ideia, to add's this post. The my application and situations. FIFO [Firts-in-Firts-out] - can exist matrix of 1 or more dimension (Says, elements that can be parameters: width, length, weight, etc.) Situations: A) Always in a system, that enters an object, is worked, and I left in the end from the line, where not the possibility of discard from the line. B) When needs accumulate pieces, that are captured by be not inside the parameters required in the moment. (Acumulador vertical) Application: A) Wood- Measures thickness and length in him I initiate, and in the end prints label with the measures. B) warehouse- Where guard objects, and entrance /exit by the same extremity. SHIFT- can have 2n bits, rotating for left or right. Situations: Store busy/free positions, and accompany displacements. Application: A) machine, where the sensor grasps the object in the entrance, and this enters in the carrosel. Being able to otimize the operation, eliminating actions for free positions. B) accompaniments of products: b1)Can have an operation fails (Ex: Fails, in the placement from the cover) b2)They should be ignored, and follow for the line do not receive operations. b3)Object peculiar, that needs combination of actions peculiar. ROTATE - Always (Certain!?) of entire number of Bytes, crazy for left or right. Situations - Someone is able to he tell by me??? Application: Only I utilized, in a machine tool. Where 2 existed circles and in the perimeter the tools. The circles of position intersetion of the internal perimeter, and overlapping So that rotation in an each position I circulate, combined the tools to a rotation/torque and way of rotate. I consider , these important instructions and a salvation for situations complicated (not complex), knowing and imagining combinations, overlapping , obtains creative results, and quick. I cite, a machine for operations in pieces of wood, that cuts, sandpapers, penetrates and border the tips for sizes and agreed, peculiar kinds of pieces that traverses in the mat. Intercalate FIFO, SHIFT and SEQUENCIATOR, without think a lot, the machine functioned in 2:30h-3h, I left I laugh, very satisfied stayed that I went although say concluded in the following day. I expect that the considerations of the colleagues, and application that will utilize these instructions. Important: THE instruction FIFO: should add interlock, for that in the same SCAN not the trigger occur of input & output.
Posted
I take it you are asking what others think about using buffers, stacks, etc in machine control? Hopefully I havn't missed your point entirely. :) Personally I'm of 2 minds about it. I think it can be a bad practice if not used carefully. It can lead to bugs that are difficult to diagnose. On the other hand, there are ways of doing it that work well (at least for me). I tend to not use built-in functions for operating on buffers. Rather, I asign a section of memory for use as a buffer area and then I asign an integer as a pointer into the buffer. I then increment/decrement the pointer and use it as an offset. I can set limits for the pointer and using compare instructions, keep it under control. I feel this gives me a more visible and less error prone method of operating. Actually, now that you mention it, I probably use something like this in almost every project so I guess I'm a big fan of it. ;) Jim Rowell
Posted
Hello! I thank, by the arrangement from the answer. Yes, it would like comments of others programmers about the use of these instructions, and situations that were applied with efficiency. But, it looks big part that only capable of answer with ready answers. JimRowell I agree that should utilize you are intrutions with take care, due to operate with memory, the records of control should be guarded, limited in the reach (encapsulate you go ideal term). I like of exploit the instructions and diverse capacities of several PLC' s, carrying out diverse compositions of instructions, and mainly trying uncover fails hides it. Perhaps, this be, the factor of fear of the frequent use of these instructions, therefore soon that perceives fails it, bug, abandons the use. These bugs they exist, created by the users or belonging to the firware or to internal same in level of processing, this would generate another post.
Posted
I’ve used the FIFO and BSL/R functions in the AB PLC and SLC plc’s to track the number of parts or presence of part on conveyor systems for coating and curing of parts. I’ve saved time in coding and memory allocation. When writing code prior to final design or in copy and paste this is a proven method. When putting a batch of parts together or collecting data the FIFO provides load and data position signals. The chances of someone over writing your data are reduced. I’ve used in taking averages for process control in SLC’s. The load and unload functions work for the rotate of tools or parts thru a process. The unload bit goes to the load bit. With tying the unload and load steps in the same rung the FIFO length is held constant. This is essential in drying oven. Moving the data in one direction is part on the functions operation. Moving the data in the opposite direction takes a little planning. The FIFO needs to have open address in the start and finish positions required. The number depending on the reverse shift required. The triggers for load remain same with an added move statement to push the data in the required position in the stack. The only difference in the unload, instead of monitoring the unload word the unload position is checked. The data reverse is handled with a scan function, a move statement and some indirect addressing, to move the data down one position in the stack. The FIFO operation needs to be locked out during this step. Functions are our friends.

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