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XRT79L71
PRELIMINARY
423
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
STEP 3 - Configure the XRT79L71 to operate in the E3, ITU-T G.832 Framing Format
To configure the XRT79L71 to operate in the E3, ITU-T G.832 Framing format write the appropriate data into
Bits 2 (IsDS3) and 6 (Frame Format) within the Framer Operating Mode Register (Address = 0x1100), as
depicted below.
The following table lists the relationship between the value of these bit-fields and the resulting framing format
for the XRT79L71.
he XRT79L71 will be operating in the E3, ITU-T G.751 Framing Format, upon power-up or hardware reset.
Therefore, the user must set Bit 6 (Frame Format) to "1" in order to configure the XRT79L71 to operate in the
E3, ITU-T G.832 Mode.
NOTE: This bit setting configures the framing format for both the Transmit DS3/E3 Framer block and the Receive DS3/E3
Framer block.
Definition of the E3, ITU-T G.832 Overhead Bytes
In general, the E3, ITU-T G.832 Overhead bytes serve the following three purposes.
1.
To support Frame Synchronization between the Near-End and remote E3 Terminals.
2.
To provide Bit-Interleaved-Parity bits in order to facilitate performance monitoring and error detection with
the E3 data-stream.
3.
To support the transmission of Alarms, Status, and Data Link Information between the Near-End and the
remote E3 Terminals.
Payload HDLC Control Register, Address = 0x1182
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framer
By-Pass
HDLC
Controller
Enable
HDLC
CRC-32
Unused
HDLC
Loop-back
Unused
R/W
R/O
R/W
R/O
0
Framer Operating Mode Register (Address = 0x1100)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Local Loop
Back
IsDS3
Internal LOS
Enable
RESET
Direct
Mapped
ATM
Frame For-
mat
TimRefSel[1:0]
R/W
0
1
0
1
TABLE 52: THE RELATIONSHIP BETWEEN THE CONTENTS OF BITS 2 (FRAME FORMAT) AND 6 (ISDS3) WITHIN THE
FRAMER OPERATING MODE REGISTER, AND THE RESULTING FRAMING FORMAT
BIT 6 (ISDS3)
BIT 2 (FRAME FORMAT)
RESULTING FRAMING FORMAT OF XRT79L71
0
E3, ITU-T G.751
0
1
E3, ITU-T G.832
1
0
DS3, C-bit Parity
1
DS3, M13/M23