XRT7250 datasheet(387/463 Pages) EXAR

387 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

368

within the Tx E3 Configuration Register, as depicted

below.

)

If the user writes a “0” into this bit-field, then the

LAPD Transmitter will transmit the comprising octets

of the Outbound LAPD Message frame via the GC

byte field. Additionally, the Transmit E3 Framer block

will insert the contents of the TxNR Byte Register

(Address = 0x37) into the “NR” byte of each Out-

bound E3 frame.

Conversely, if the user writes a “1” into this bit-field,

then the LAPD Transmitter will transmit the Outbound

LAPD Message frame octets via the NR byte-field,

within each Outbound E3 frame. Additionally, the

Transmit E3 Framer will insert the contents of the Tx

GC Byte Register (Address = 0x35) into the GC byte-

field of each Outbound E3 frame.

STEP 5 - Specify whether the LAPD Transmitter

should transmit the LAPD Message frame only

once, or an indefinite number of times at One-

Second intervals.

The Transmit E3 HDLC Control block allows the user

to configure the LAPD Transmitter to transmit this

LAPD Message frame only once, or an indefinite

number of times at One-Second intervals. The user

implements this configuration by writing the appropri-

ate value into Bit 3 (Auto Retransmit) within the Tx E3

LAPD Configuration Register (Address = 0x33), as

depicted below.

)

If the user writes a “1” into this bit-field, then the

LAPD Transmitter will transmit the LAPD Message

frame repeatedly at One-Second intervals until the

LAPD Transmitter is disabled.

If the user writes a “0” into this bit-field, then the

LAPD Transmitter will transmit the LAPD Message

frame only once. Afterwards, the LAPD Transmitter

will halt its transmission until the user invokes the

Transmit LAPD Message frame command, once

again.

STEP 6 - Enabling the LAPD Transmitter

Prior to the transmission of any data via the LAPD

Transmitter, the LAPD Transmitter must be enabled

by writing a "1" to bit 0 (TxLAPD Enable) of the Tx E3

LAPD Configuration Register, as depicted below.

TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)

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

Not Used

TxDL

in NR

Not Used

TxAIS

Enable

TxLOS

Enable

TxMARx

R/W

000

TXE3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)

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

Not Used

Auto

Retransmit

Not Used

TxLAPD

Msg Length

TxLAPD

Enable

R/W

001

000

TRANSMIT E3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT2BIT 1

BIT 0

Not Used

Auto

Retransmit

Not Used

TxLAPD

Msg Length

TxLAPD

Enable

R/O

R/W

R/O

R/W

XRT7250 Datasheet(PDF) 387 Page - Exar Corporation

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