XRT7250 Datasheet, PDF (79/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250 DS3/E3 FRAMER IC
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REV. 1.1.1
The XRT7250 will set this bit-field to "0" if it is not cur-
rently detecting an AIS pattern in the incoming data
stream. Conversely, the XRT7250 will set this bit-field
to "1" if it is currently receiving an AIS pattern in the
incoming data stream.
NOTE: For a more detailed discussion on the AIS pattern
for DS3 applications, please see Section 3.3.2.5.2
Bit 6 - RxLOS (Receive LOS Condition) Indicator
This Read-Only bit-field indicates whether or not the
Receive Section of the Framer device is currently de-
claring an LOS (Loss of Signal) condition of the in-
coming DS3 or E3 data stream.
If this bit-field is set to "0", then the Receive Section
(of the chip) is currently not declaring an LOS condi-
tion.
If this bit-field is set to "1", then the Receive Section
(of the chip) is currently declaring an LOS condition.
NOTE: For more information on the LOS Declaration crite-
ria, for DS3 and E3 applications, please see Section
3.3.2.5.2.
Bit 5 - RxIdle (Receive Idle Pattern) Indicator
This Read-Only bit-field indicates whether or not the
Receive Section of the Framer device is currently de-
tecting the Idle-pattern in the incoming DS3 data
stream.
If this bit-field is set to "0" then the Receive Section
(of the chip) is currently not detecting the Idle-pattern
in the incoming DS3 data stream.
If this bit-field is set to "1" then the Receive Section
(of the chip) is currently detecting the Idle pattern in
the incoming DS3 data stream.
NOTES:
1. This bit-field is only relevant for DS3 applications.
2. For more information on the Idle Pattern, please
see Section 3.3.2.5.3
Bit 4 - RxOOF (Receive Out-of-Frame) Indicator
This Read-Only bit-field indicates whether or not the
Receive Section of the Framer device is currently de-
claring an OOF (Out of Frame) condition.
If this bit-field is set to "0", then the Receive Section
(of the chip) is currently not declaring the OOF condi-
tion.
If this bit-field is set to "1", then the Receive Section
(of the chip) is currently declaring the OOF condition.
NOTE: For more information on the OOF Declaration crite-
ria, for DS3 applications, please see Section 3.3.2.2.
Bit 3 - Reserved.
Bit 2 - Framing On Parity ON/OFF Select
This Read/Write bit field allows the user to require
that the Receive DS3 Framer include Parity (P-bit)
verification as a condition for declaring itself In-
Frame, during Frame Acquisition. This requirement
will be imposed in addition to those criteria selected
via Bits 0 and 1 of this register.
This feature also imposes an additional Frame Main-
tenance requirement on the Receive DS3 Framer, in
addition to the requirements specified in the user's
selection of Bits 0 and 1 of this register. In particular,
if this additional requirement is implemented, the Re-
ceive DS3 Framer will perform a frame search if it de-
tects P-bit errors in at least 2 out of 5 DS3 Frames.
Writing a "1" to this bit-field imposes these additional
requirements. Whereas, writing a '0' causes the Re-
ceive DS3 Framer to waive this requirement.
NOTE: For more information on Framing with Parity please
see Section 3.3.2.2.
Bit 1 - F Sync Algo(rithim Select)
This 'Read/Write' bit-field, in conjunction with Bits 0
and 2 of this register, allows the user to completely
define the Frame Maintenance Criteria of the Receive
DS3 Framer. This particular bit-field allows the user
to define the Frame Maintenance Criteria as it applies
to F-bits.
If the user writes a "1" to this bit-field, then the Re-
ceive DS3 Framer will declare an Out of Frame (OOF)
condition if 3 out of 16 F-Bits are in Error. If the user
writes a "0" to this bit-field, then the Receive DS3
Framer will declare an Out of Frame (OOF) condition
is 6 out of 16 F-bits are in error.
NOTE: For more information on the use of this bit, and the
Framing Maintenance operation of the Receive DS3
Framer, please see Section 3.3.2.2.
Bit 0 - M Sync Algo(rithm Select)
This 'Read/Write' bit-field in conjunction with Bits 1
and 2 of this register, allows the user to completely
define the Frame Maintenance Criteria of the Receive
DS3 Framer. This particular bit-field allows the user
to define the Frame Maintenance criteria, as it applies
to M-bits.
If the user writes a "1" to this bit-field, then the Re-
ceive DS3 Framer will declare an Out of Frame (OOF)
condition if 3 out of 4 M-bits are in error. If the user
writes a "0" to this bit-field, then the Receive DS3
Frame will ignore the occurrence of M-bit errors while
operating in the Frame Maintenance mode.
NOTE: For more information on the use of this bit-field, and
the Framing Maintenance operation of the Receive DS3
Framer, please see Section 3.3.2.2.
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