Fll instruction in rs logix 5000

Hi guys;
please guide me how the FLL instruction work?
the example is given below
source=0
destination=PGM_SEQUENCE
LENGTH=1
I AM UNABLE TO UNDERSTAND HOW THIS WORK PLEASE HELP ME ON THIS ISSU
THANKS

The matter is for understanding is length.
The destination tag PGM_SEQUENCE have 23 items for example
PGM_SEQUENCE.START,PGM_SEQUENCE.SHUTDOWN and etc;
but the value of length is 1, i can not understand that please help me

The length is the number of elements to fill, of the data type given in destination. So if you have an array of 10 ints, then length could be 1 - 10 depending on howmany you want to do.

If the type is a not an array or even a structure / UDT, then the number of items is 1, as it's just an array of 1. It could just as easily be an array of PGM_SEQUENCE, then you could use length > 1 to clear them all in 1 instruction.