GN_Flr, Read character from filter

Register parameters

RST 20H, DEFW $2809
IN:
     IX = filter handle

OUT, if call successful:
     Fc = 0
     A = character read from filter
     Fz = 1, if character is converted, else unconverted, Fz = 0.

OUT, if call failed:
     Fc = 1
     A = error code:
          RC_HAND ($08), bad filter handle
          RC_EOF ($09), filter is empty

Registers changed after return:
     ..BCDEHL/IXIY same
     AF....../.... different 

Related calls

GN_Flc, close filter
GN_Flf, flush filter
GN_Flo, open filter
GN_Flw, write character to filter
GN_Fpb, push back into filter