S5 AWL Commands: BE, BEA, BEB (Block End)

S5 AWL uses three block-end instructions. Every block must end with BE (or BEA). BEB provides conditional block exit.

BE — Block End (Bausteinende)#

The standard block-end instruction. Mandatory at the end of every S5 block (OB, FB, FC, DB).

U  E 0.0
=  A 4.0
BE              // End of block — return to calling block

S7 equivalent: BE is automatic in S7 TIA Portal — you do not write it explicitly. In S7 STL, BE still exists but is optional.

BEA — Block End Absolute (Bausteinende absolut)#

Identical to BE. Returns to the calling block unconditionally. In practice, BEA and BE are interchangeable in most S5 CPUs. BEA is sometimes used to emphasize "this is a definitive end."

BEA             // Same as BE in most CPUs

BEB — Block End Conditional (Bausteinende bedingt)#

Ends the block only if VKE is TRUE. If VKE is FALSE, execution continues with the next instruction. Used for "early exit" patterns.

U   E 0.5          // Check condition
BEB                 // If TRUE → exit block immediately
// ... code below only runs if E 0.5 is FALSE ...
BE

S7 equivalent: IF condition THEN RETURN; END_IF; in SCL.

Common Error#

Forgetting BE at the end of a block: Without BE, the CPU may execute random memory as instructions, causing unpredictable behavior or a CPU STOP.

Related: SPA FB (Call FB) | SPA PB (Call PB)#

Part of the S5 AWL Command Reference. Maintained by PLCcheck.ai.

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