Fast Information Block - mattpascoe135/dab GitHub Wiki

#Fast Information Block The general structure of the FIB is shown in figure 3, for a case when the useful data does not occupy the whole of a FIB data field. The FIB contains 256 bits and comprises an FIB data field and a CRC.

The FIG data can be seen Here

##FIB data field: the FIB data field shall be organized in bytes allocated to useful data, an end marker and padding in the following way:

• the useful data occupy the whole 30 bytes of the FIB data field. In this case, there shall be no end marker and no padding bytes;
• the useful data occupy 29 bytes of the FIB data field. In this case, there shall be an end marker but no padding bytes;
• the useful data occupy less than 29 bytes. In this case, there shall be both an end marker and padding bytes;
• there is no useful data. In this case, the FIB data field shall begin with an end marker and the rest of the FIB data field contains padding bytes.

The FIB data field is described as follows: ###Useful data field: this contains one or more Fast Information Groups (FIGs) (see clause 5.2.2).

###End marker: is a special FIG and shall have a FIG header field (111 11111) and no FIG data field.

###Padding: this field shall contain the bytes required to complete the FIB data field. The padding byte field shall contain all zeroes.

###CRC: a 16-bit Cyclic Redundancy Check word is calculated on the FIB data field and shall be generated according to the procedure defined in annex E. The generation shall be based on the polynomial

`G(x) = x^16 + x^12 + x^5 + 1`

At the beginning of each CRC word calculation, all shift register stage contents shall be initialized to "1". The CRC word shall be complemented (1's complement) prior to transmission.