6. Function blocks6.3 UF - User function block6.3 UF - User function blockOnly possible with easySoft 7.6.3.1 GeneraleasyE4 base devices provide 127 user function blocks, UF01 throughUF127.You can configure these function blocks yourself and then use themin the main program the same way as manufacturer function blocks.User function blocks are used whenever a recurring functionality needs to be pro-grammed with various parameters. For example, when similar machines need to becontrolled, the actual control program for them can be written in a user function blockand then called multiple times – separately for each machine. User function blocks alsofeature inputs and outputs that can be used to pass custom parameters for each call.The programming language used in each user function block is independent from theprogramming language used for the corresponding main program. In other words, youcan use user function blocks written in ST in an FBD or LD main program, for instance.User function blocks have their own data range. In fact, there are 64 bytes, which canbe used as bits, bytes, words, or double words, available for each instance (call) of auser function block. This means, for example, that marker M01 in the main program isnot the same marker M01 in a user function block.Parts of the markers can be declared as being retentive. In this case, it is important tokeep in mind that the total number of retentive markers cannot exceed 400 bytes, andthat this total includes the retentive markers from the main program and the retentivemarkers from all user function block instances.Just like a main program, a user function block is made up of FBD/LD networks or STsource code. This means that a user function block can be created the same way as amain program, with the only differences consisting of the available operands (pleaserefer to → Section "Configuring a user function block", page 435.The maximum number of user function blocks that can be called in a single main pro-gram is 127.432 easyE4 11/18 MN050009 EN www.eaton.com
