XRT7250 datasheet(79/463 Pages) EXAR

79 / 463 page

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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