XRT7250 Datasheet, PDF (147/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250 DS3/E3 FRAMER IC
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REV. 1.1.1
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
FIGURE 41. DS3 FRAME FORMAT FOR M13
X
I
F1
I C11 I
F0
I C12 I
F0
I C13 I
F1
I
I
X
I
F1
I C21 I
F0
I C22 I
F0
I C23 I
F1
I
P
I
F1
I C31 I
F0
I C32 I
F0
I C33 I
F1
I
P
I
F1
I C41 I
F0
I C42 I
F0
I C43 I
F1
I
M0
I
F1
I C51 I
F0
I C52 I
F0
I C53 I
F1
I
M1
I
F1
I C61 I
F0
I C62 I
F0
I C63 I
F1
I
M0
I
F1
I C71 I
F0
I C72 I
F0
I C73 I
F1
I
X = Signaling bit for network control
Mi = multiframe synchronization bit with logic values i
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
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.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local Loopback
R/W
x
DS3/E3*
R/W
1
Internal LOS
Enable
R/W
x
RESET
R/W
0
Interrupt
Enable Reset
R/W
x
Frame Format
R/W
x
TimRefSel[1:0]
R/W
R/W
x
x
Table 16 lists the relationship between the value of
the this bit-field and the resulting DS3 Frame Format.
TABLE 16: THE RELATIONSHIP BETWEEN THE CONTENT
OF BIT 2, (C-BIT PARITY*/M13) WITHIN THE FRAMER
OPERATING MODE REGISTER AND THE RESULTING DS3
FRAMING FORMAT
BIT 2
0
1
DS3 FRAME FORMAT
C-Bit Parity
M13
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
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