Chapter 4. Ladder Diagram (LD) ProgrammingGFK-2950C February 2018 2034.11.2 CallNon-parameterized Parameterized. May call a parameterized external block or a parameterizedblock. May have up to 7 input and 8 output parameters.When the CALL function receives power flow, it causes the logic execution to go immediately to thedesignated program block, external C block (parameterized or not), or parameterized block andexecute it. After the block’s execution is complete, control returns to the point in the logicimmediately following the CALL instruction.Notes:▪ A CALL function can be used in any program block, including the _MAIN block, or a parameterizedblock. It cannot be used in an external block.▪ You cannot call a _MAIN block.▪ The called block must exist in the target before making the call.▪ There is no limit to the number of calls that can be made from or to a given block.▪ You can set up recursive subroutines by having a block call itself. When stack size is configuredto be the default (64K), the PLC guarantees a minimum of eight nested calls before anApplication Stack Overflow fault is logged.▪ Each block has a predefined parameter, Y0, which the CPU sets to 1 upon each invocation of theblock. Y0 can be controlled by logic within the block and provides the output status of the block.When the Y0 parameter of a Program Block, parameterized block, or external C block returns ON,the CALL passes power to the right; when it returns OFF, the CALL does not pass power to theright.
