XRT7250 datasheet(147/463 Pages) EXAR

147 / 463 page

XRT7250

DS3/E3 FRAMER IC

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REV. 1.1.1

128

Fi = Frame synchronization bit with logic value i

P = Parity bit

Mi = Multiframe synchronization bit with logic value i

AIC = Application Identification Channel

NA = reserved for network application

FEAC = Far End Alarm and Control

DL = Data Link

CP = CP (Path)-bit parity

FEBE = Far End Block Error

UDL = User Data Link

X = Signaling bit for network control

I = Payload Information (84 bit packets)

Fi = Frame synchronization bit with logic value i

Cij = jth stuff code bit of ith channel

P = Parity bit

Mi = multiframe synchronization bit with logic values i

The user can choose between these two frame for-

mats, by writing the appropriate data to bit 2 of the

Framer Operating Mode Register (Address = 0x00),

as depicted below.

Table 16 lists the relationship between the value of

the this bit-field and the resulting DS3 Frame Format.

NOTE: This bit setting also configures the frame format for

both the Transmit and Receive Section of the XRT7250.

Each of the two DS3 Frame Formats, as presented in

Figure 40 and Figure 41, constitute an M-frame (or a

full DS3 Frame). Each M-frame consists of 7 - 680 bit

F-frames (sometimes referred to as, subframes). In

Figure 40 and 41, each F-frame is represented by

the individual rows of payload and overhead bits.

Each F-frame can be further divided into 8 blocks of

85 bits, with 84 of the 85 bits available for payload in-

formation and the remaining one bit used for frame

overhead.

Differences Between the M13 and C-Bit Parity

Frame Formats

The frame formats for M13 and C-bit Parity are very

similar. However, the main difference between these

FIGURE 41. DS3 FRAME FORMAT FOR M13

IF1

IC11

IF0

IC12

IF0

IC13

IF1

IC21

IF0

IC22

IF0

IC23

IF1

IC31

IF0

IC32

IF0

IC33

IF1

IC41

IF0

IC42

IF0

IC43

IF1

IC51

IF0

IC52

IF0

IC53

IF1

IC61

IF0

IC62

IF0

IC63

IF1

IC71

IF0

IC72

IF0

IC73

IF1

FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)

BIT 7

BIT 6BIT 5BIT 4BIT 3

BIT2BIT 1BIT 0

Local Loopback

DS3/E3*

Internal LOS

Enable

RESET

Interrupt

Enable Reset

Frame Format

TimRefSel[1:0]

R/W

TABLE 16: THE RELATIONSHIP BETWEEN THE CONTENT

BIT 2, (C-BIT PARITY*/M13) WITHIN THE FRAMER

OPERATING MODE REGISTER AND THE RESULTING DS3

FRAMING FORMAT

BIT 2

DS3 FRAME FORMAT

C-Bit Parity

1M13

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