Remove RETAIN qualifier for F_TRIG and R_TRIG 'M' variable. This is not following standard, and implicitely consumes a lot of RETAIN memory. User can explicitely qualify R_TRIG of F_TRIG instance as RETAIN if needed.
FUNCTION WEIGH : WORD (* BCD encoded *)
VAR_INPUT (* "EN" input is used to indicate "scale ready" *)
weigh_command : BOOL;
gross_weight : WORD ; (* BCD encoded *)
tare_weight : INT ;
END_VAR
(* Function Body *)
LD weigh_command
JMPC WEIGH_NOW
ST ENO (* No weighing, 0 to "ENO" *)
RET
WEIGH_NOW: LD gross_weight
BCD_TO_INT
SUB tare_weight
INT_TO_BCD (* Return evaluated weight *)
ST WEIGH
END_FUNCTION (* Implicit "ENO" *)