Cmi (code mark inversion) option, 6 cmi (c, Nversion – Rainbow Electronics DS21458 User Manual
Page 163: Ption, Figure 25-4. cmi coding, 6 cmi (code mark inversion) option
DS21455/DS21458 Quad T1/E1/J1 Transceivers
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25.6 CMI (Code Mark Inversion) Option
The DS21455/DS21458 provide a CMI interface for connection to optical transports. This interface is a
unipolar 1T2B type of signal. Ones are encoded as either a logical one or zero level for the full duration
of the clock period. Zeros are encoded as a zero-to-one transition at the middle of the clock period.
Figure 25-4. CMI Coding
Transmit and receive CMI is enabled via LIC4.7. When this register bit is set, the TTIP pin will output
CMI-coded data at normal levels. This signal can be used to directly drive an optical interface. When
CMI is enabled, the user can also use HDB3/B8ZS coding. When this register bit is set, the RTIP pin will
become a unipolar CMI input. The CMI signal will be processed to extract and align the clock with data.
0
1
1
1
0
0
1
CLOCK
DATA
CMI