GE PACSystems RXi User Manual

Chapter 6. Program Organization100 PACSystems* RXi Distributed IO Controller User Manual GFK-2816FProgram BlocksAny block can be a program block. The _MAIN block is automatically declared when youcreate a block-structured program. When you declare any other block, you must assign it aunique block name. A block is automatically configured with no input parameters and oneoutput parameter (OK).When a block-structured program is executed, the _MAIN block is automatically executed.Other blocks execute when called from the program logic in the _MAIN block, another block,or itself. In the following example, if %M00001 is ON, the block named Process1 is executed:Program Blocks and Local DataProgram blocks support the use of %P global data. In addition, each block, except _MAIN,has its own %L local data. Blocks do not inherit %L local data from their callers.Using Parameters with a Program BlockEvery block is automatically defined with one formal ‘power flow’ (or OK) output parameternamed Y0. Y0 is a BOOL parameter of LENGTH 1, passed by initial-value result. It indicatessuccessful execution of the block. It can be read and written to by the logic within the block.