GMSK Packet Data Modem
CMX909B
Figure 13 Interleaving - Input/Output
1.5.5.4 Scrambling
All formatted bits of both Mobitex Data Blocks and Short Data Blocks are passed through a 9-bit
scrambler. This scrambler is initialised at the beginning of the first data block in every Frame. The
511-bit sequence is generated with a 9-bit shift register with the output of the 5th and 9th stages
XOR’ed and fed back to the input of the first stage. The scrambler is disabled during all other tasks,
apart for TSO.
ã 2001 Consumer Microcircuits Limited
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D/909B/1