XRT7250 datasheet(84/463 Pages) EXAR

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

2.3.2.13 Receive DS3 LAPD Control Register

Bit 2 RxLAPD Enable

This Read/Write bit-field allows the user to enable or

disable the LAPD Receiver. The LAPD Receiver

MUST be enabled before it can begin to receive and

process any LAPD Message frames from the incom-

ing DS3 data stream.

Writing a "0" to this bit-field disables the LAPD Re-

ceiver (the default condition). Writing a "1" to this bit-

field enables the LAPD Receiver.

Bit 1 RxLAPD (Message Frame Reception Com-

plete) Interrupt Enable

This Read/Write bit-field allows the user to enable or

disable the LAPD Message Frame Reception Com-

plete interrupt. If this interrupt is enabled, then the

UNI will generate this interrupt to the local µP, once

the last bit of a LAPD Message frame has been re-

ceived and the PMDL message has been extracted

and written into the Receive LAPD Message buffer.

Writing a "0" to this bit-field disables this interrupt (the

default condition). Writing a "1" to this bit-field en-

ables this interrupt.

Bit 0 RxLAPD (Message Reception Complete) In-

terrupt Status

This Read-Only bit field indicates whether or not the

LAPD Message Reception Complete interrupt has

occurred since the last read of this register. The

LAPD Message Reception Complete interrupt will oc-

cur once the LAPD Receiver has received the last bit

of a complete LAPD Message frame, extracted the

PMDL message from this LAPD Message frame and

has written this (PMDL) message frame into the Re-

ceive LAPD Message buffer. The purpose of this in-

terrupt is to notify the local µP that the Receive LAPD

Message buffer contains a new PMDL message, that

needs to be read and/or processed.

A "0" in this bit-field indicates that the LAPD Message

Reception Complete interrupt has NOT occurred

since the last read of this register. A "1" in this bit-

field indicates that the LAPD Message Reception

Complete interrupt has occurred since the last read of

this register.

NOTE: For more information on the LAPD Receiver, please

see Section 3.3.3.2.

2.3.2.14 Receive DS3 LAPD Status Register

Bit 6 - RxAbort (Receive Abort Sequence)

This Read-Only bit-field indicates whether or not the

LAPD Receiver has detected the occurrence of an

Abort Sequence (e.g., a string of seven or more con-

secutive "1’s") from the far-end LAPD Transmitter. A

"0" in this bit-field indicates that no Abort-Sequence

has been detected. A "1" in this bit-field indicates that

the Abort-Sequence has been detected.

NOTE: For more information on the LAPD Receiver, please

see Section 3.3.3.2.

Bits, 5 and 4 - RxLAPDType[1, 0]

These two Read Only bit-fields combine to indicate

the type of LAPD Message frame that has been re-

ceived by the LAPD Receiver. The relationship be-

RXDS3 LAPD CONTROL REGISTER (ADDRESS = 0X18)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0

Not Used

RxLAPD

Enable

RxLAPD

Interrupt

Enable

RxLAPD

Interrupt

Status

R/W

RUR

0000

000

RXDS3 LAPD STATUS REGISTER (ADDRESS = 0X19)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0

Not Used

RxAbort

RxLAPDType[1:0}

RxCR Type

RxFCS Error

End of

Message

Flag Present

0000

000

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