etisserant@0: FUNCTION_BLOCK STACK_INT
etisserant@0:   VAR_INPUT PUSH, POP: BOOL R_EDGE; (* Basic stack operations *)
etisserant@0:             R1 : BOOL ;          (* Over-riding reset *)
etisserant@0:             IN : INT ;           (* Input to be pushed *)
etisserant@0:             N  : INT ;           (* Maximum depth after reset *)
etisserant@0:   END_VAR
etisserant@0:   VAR_OUTPUT EMPTY : BOOL := 1 ;     (* Stack empty *)
etisserant@0:              OFLO  : BOOL := 0 ;     (* Stack overflow *)
etisserant@0:              OUT   : INT  := 0 ;     (* Top of stack data *)
etisserant@0:   END_VAR
etisserant@0:   VAR STK : ARRAY[0..127] OF INT; (* Internal stack *)
etisserant@0:       NI : INT :=128  ;           (* Storage for N upon reset *)
etisserant@0:       PTR : INT := -1 ;           (* Stack pointer *)
etisserant@0:   END_VAR
etisserant@0:     (* Function Block body *)
etisserant@0:     IF R1 THEN
etisserant@0:        OFLO := 0; EMPTY := 1; PTR := -1;
etisserant@0:        NI := LIMIT (MN:=1,IN:=N,MX:=128); OUT := 0;
etisserant@0:     ELSIF POP & NOT EMPTY THEN
etisserant@0:        OFLO := 0; PTR := PTR-1; EMPTY := PTR < 0;
etisserant@0:        IF EMPTY THEN OUT := 0;
etisserant@0:        ELSE OUT := STK[PTR];
etisserant@0:        END_IF ;
etisserant@0:     ELSIF PUSH & NOT OFLO THEN
etisserant@0:        EMPTY := 0; PTR := PTR+1; OFLO := (PTR = NI);
etisserant@0:        IF NOT OFLO THEN OUT := IN ; STK[PTR] := IN;
etisserant@0:        ELSE OUT := 0;
etisserant@0:        END_IF ;
etisserant@0:     END_IF ;
etisserant@0: 
etisserant@0:   END_FUNCTION_BLOCK