The FB is a function intended to exchange a ladder block, it is to use in a program sequence constantly, into a FB to use it in the chain program. This not only enlarges the program development efficiency but also decreases mistakes of programming to get better quality of program.
The FB has the below features.
(1) Exchange of program into component
Showing a program standardization as a single block recovers the readability and reuse of the program, debugging and facilitating editing. This guarantees simplicity of configuring a large-scale program.
(2) Quality of uniform program
Reuse the standard program components offers quality of uniform program, which is free of the level of technological program developer. It also avoids programming mistakes during operation. (3) High operability editing function
The FB can be operated simply in a sequence program by operation of drag and drop.
1) The FB can not be utilized within the FB.
2) Online program improvement can not be created to the program sequence that comprises the FB when the definition program of FB has been corrected. When lettering the program sequence plus the corrected FB to the CPU of PLC, carry out write to PLC in the mode of online.
3) Index qualification is not available for labels.
Utilize a real device as the target device to create qualification index.
4) If a variable internal is utilized as the division instruction result, its remains can not be utilized for control because a label can not be allocated to the division remainder. To utilize the remainder of an instruction division for control, use an actual device as the device for saving the result of division.
5) Because the device of numerical that may be handling by a variable input is up to a two times word, the instruction go above 3 words in count of input can not be input from the external. To input 3 or more words from the outside, apply a real device as the tool for saving an input value or create the input instructions by the required times number.
6) Since the arithmetic device that might be switched by a variable of output is equal to a twice word, the order with result will be three or more words can not be output to the outside. To output 3 or more words to the outside, utilize an real tool as the device for saving the result.