Datasheet

DS21Q58 E1 Quad Transceiver

53 of 74

22. CODE MARK INVERSION (CMI)

The DS21Q58 provides a CMI interface for connecting to optical transports. This interface is a unipolar 1T2B-

coded signal. Ones are alternately encoded as a logical 1 or 0 level for the full duration of the clock period. Zeros

are encoded as a 0-to-1 transition at the middle of the clock period. Figure 22-1

shows an example data pattern

and its CMI result. The control bit for enabling CMI is in the OUTAC register, as shown below.

OUTAC

OUTA Control Register

1A Hex

Bit # 7 6 5 4 3 2 1 0

Name TTLIE CMII CMIE OA4 OA3 OA2 OA1 OA0

NAME BIT FUNCTION

TTLIE 7

TTL Input Enable. When this bit is set, the receiver can accept TTL

positive and negative data at the RTIP and RRING inputs. The data is

clocked in on the falling edge of MCLK.

CMII 6

CMI Invert

0 = CMI input data not inverted

1 = CMI input data inverted

CMIE 5

Transmit and Receive CMI Enable

0 = Transmit and receive line interface operates in normal AMI/HDB3 mode/

1 = Transmit and receive line interface operate in CMI mode. TTIP is CMI

output and RTIP is CMI input. In this mode of operation TRING and RRING

are not connected.

OA4 4

OUTA Control Bit 4. Inverts OUTA output.

OA3 3

OUTA Control Bit 3. See Table 20-1

for details.

OA2 2

OUTA Control Bit 2. See Table 20-1

for details.

OA1 1

OUTA Control Bit 1. See Table 20-1

for details.

OA0 0

OUTA Control Bit 0. See Table 20-1

for details.

Figure 22-1. CMI Coding

0 1 1 1 0 0 1

CLOCK

DATA

CMI