Communication Processor Module
16-196 MPC823e REFERENCE MANUAL MOTOROLA
SCCs
COMMUNICATION
16
PROCESSOR MODULE
16.9.11.1 ENCODING AND DECODING DATA WITH A DPLL. Each serial
communication controller contains a digital phase-locked loop unit that can be programmed
to encode and decode SCCx data as NRZ, NRZI Mark, NRZI Space, FM0, FM1,
Manchester, and Differential Manchester. Examples of the different encoding methods are
illustrated in Figure 16-72.
If you do not want to use the DPLL, you can choose NRZ coding in the RENC and TENC
bits of the GSMR_L. The coding is defined as follows:
• NRZ—A one is represented by a high level for the duration of the bit and a zero is
represented by a low level.
• NRZI Mark—A one is represented by no transition at all. A zero is represented by a
transition at the beginning of the bit (the level present in the preceding bit is reversed).
• NRZI Space—A one is represented by a transition at the beginning of the bit (the level
present in the preceding bit is reversed). A zero is represented by no transition at all.
• FM0—A one is represented by a transition only at the beginning of the bit. A zero is
represented by a transition at the beginning of the bit and another transition at the
center of the bit.
• FM1—A one is represented by a transition at the beginning of the bit and another
transition at the center of the bit. A zero is represented by a transition only at the
beginning of the bit.
Figure 16-72. DPLL Encoding Examples
NRZ
NRZI MARK
FM0
FM1
MANCHESTER
011001
DATA
DIFFERENTIAL
NRZI SPACE
MANCHESTER
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