XRT72L50 Datasheet, PDF (208/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
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Rx DS3 Configuration and Status Register, (Address = 0x10)
BIT 7
RxAIS
RO
X
BIT 6
RxLOS
RO
X
BIT 5
RxIdle
RO
X
BIT 4
RxOOF
RO
X
BIT 3
Reserved
RO
X
BIT2
Framing on
Parity
R/W
X
BIT 1
BIT 0
F-Sync Algo M-Sync Algo
R/W
R/W
X
X
Table 35 relates the contents of this bit-field to the OOF Declaration criteria
TABLE 35: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (F-SYNC ALGO) WITHIN THE RX DS3
CONFIGURATION AND STATUS REGISTER, AND THE RESULTING F-BIT OOF DECLARATION CRITERIA USED BY THE
RECEIVE DS3 FRAMER BLOCK
F-SYNC ALGO (BIT 1)
0
1
OOF DECLARATION CRITERIA
OOF is declared when 6 out of 16 consecutive F-bits are in error.
OOF is declared when 3 out of 16 consecutive F-bits are in error.
NOTE: Once the Receive DS3 Framer block has declared an OOF condition, it will transition back to the F-Bit Search state
within the DS3 Frame Acquisition/Maintenance algorithm (per Figure 69).
In addition to selecting an OOF Declaration criteria for the F-bits, the following options exist for configuring the
OOF Declaration criteria based upon M-bits.
1. M-bit errors do not cause a OOF Declaration, or
2. OOF will be declared if 3 out of 4 consecutive M-bits are in error.
The selection between these two options is made by writing the appropriate value to Bit 0 (M-Sync Algo) within
the Receive DS3 Configuration and Status Register, as depicted below.
Rx DS3 Configuration and Status Register, (Address = 0x10)
BIT 7
RxAIS
RO
X
BIT 6
RxLOS
RO
X
BIT 5
RxIdle
RO
X
BIT 4
RxOOF
RO
X
BIT 3
Reserved
RO
X
BIT2
Framing on
Parity
R/W
X
BIT 1
BIT 0
F-Sync Algo M-Sync Algo
R/W
R/W
X
X
Table 36 relates the contents of this Bit Field to the M-Bit Error criteria for Declaration of OOF.
TABLE 36: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 0 (M-SYNC ALGO) WITHIN THE RX DS3
CONFIGURATION AND STATUS REGISTER, AND THE RESULTING M-BIT OOF DECLARATION CRITERIA USED BY THE
RECEIVE DS3 FRAMER BLOCK
MSYNC ALGO (BIT 0)
0
1
OOF DECLARATION CRITERIA
M-Bit Errors do not result in the declaration of OOF
OOF is declared when 3 out of 4 M-bits are in error.
The Framing on Parity Criteria for OOF Declaration
Finally, the Framer IC offers the Framing on Parity option, which also effects the OOF Declaration criteria. As
was mentioned earlier, the Framer IC allows the user to configure the Receive DS3 Framer block to detect
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