Statement List (STL) - DCE FEL ČVUT v Praze

Program Control Instructions
10.13 UC Unconditional Call
Format
Description
Status word
Example 1
UC
UC (unconditional block call) calls a logic block of the FC or
SFC type. UC is like the CALL instruction, except that you cannot transfer
parameters with the called block. The instruction saves the return address (selector
and relative address) selectors of the two current data blocks, as well as the MA bit
into the B (block) stack, deactivates the MCR dependency, creates the local data
area of the block to be called, and begins executing the called code.
BR CC 1 CC 0 OV OS OR STA RLO /FC
writes: - - - - 0 0 1 - 0
STL Explanation
UC FC6 //Call function FC6 (without parameters).
Example 2
STL Explanation
UC SFC43 //Call system function SFC43 (without parameters).
Note
When the CALL instruction is used for a function block (FB) or system function block
(SFB) an instance data block (DB no.) is expressed explicitly in the instruction. For a
call made with the UC instruction, you cannot associate a data block in the UC
address
Depending on the network you are working with, the Program Editor either generates
the UC instruction or the CC instruction during conversion from the Ladder Logic
programming language to the Statement List programming language. You should
attempt to use the CALL instruction instead to avoid errors occurring in your
programs.
Statement List (STL) for S7-300 and S7-400 Programming
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