Offset Size Name Description
-------- -------- ------------ ---------------------------------
0x00 1 Flags Filter flags:
LENGTH (0x07)
READ_GLOBAL_DATA (0x08)
READ_REGISTERS (0x10)
READ_BLOCK_LENGTH (0x20)
ADD_258_BLOCK_START (0x40)
READ_FILTER_NUM (0x80)
0x01 1 LengthExt1 Length Extension #1
Optional - only present if LENGTH is set to 6 or 7
0x02 1 LengthExt2 Length Extension #2
Optional - only present if Length is set to 7
0x03 var Code Filter code