I Want to add some details
SFWR(FXseries)=FIFW(L-CPU) = FIFO Write
SFRD(FXseries)=FIFR(L-CPU) = FIFO Read
But disadvantage of this Fb is it can only store and return "16 bit data" other data type like Continuous String [50] , Real cannot be Input to this function.
String of 2 Character that fits inside single "D" data register is possible (IMG JPEG - FIFO-1 and FIFO -2 )