XRT7250 datasheet(106/463 Pages) EXAR

106 / 463 page

áç

DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

Bit 3 - Auto Retransmit

This Read/Write bit-field allows the user to configure

the LAPD Transmitter to either transmit the LAPD

Message frame only once or, repeatedly at one-sec-

ond intervals.

Writing a "0" to this bit-field configures the LAPD

Transmitter to transmit the LAPD Message frame

once. Afterwards, the LAPD Transmitter will halt

transmission, until it has commanded to transmit an-

other LAPD Message frame.

Writing a "1" to this bit-field configures the LAPD

Transmitter to transmit the LAPD Message frame re-

peatedly at One-Second intervals. In this configura-

tion, the LAPD Transmitter will repeat its transmission

of the LAPD Message frame until it has been dis-

abled.

Bit 1 - TxLAPD Message Length Select

This Read/Write bit-field permits the user to select

the length of the outbound LAPD Message frame.

Setting this bit-field to "0" configures the outbound

LAPD Message frame to be 76 bytes in length. Set-

ting this bit-field to “1” configures the outbound LAPD

Message frame to be 82 bytes in length.

Bit 0 - TxLAPD Enable

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

disable the LAPD Transmitter. The LAPD Transmitter

must be enabled before it can be commanded to

transmit a LAPD Message frame (containing a PMDL

message) via the outbound DS3 frames, to the Far-

End Terminal.

Writing a “0" disables the LAPD Transmitter (default

condition). Writing a "1" enables the LAPD Transmit-

ter.

NOTE: For information on the LAPD Transmitter, please see

Section 3.2.3.2.

2.3.5.5

Transmit DS3 LAPD Status and Inter-

rupt Register (DS3 Applications)

Bit 3 - TxDL Start

This Read/Write bit-field allows the user to invoke the

Transmit LAPD Message command. Once the user

invokes this command, the LAPD Transmitter will do

the following:

• Read in the PMDL Message from the Transmit

LAPD Message Buffer.

• Encapsulate the PMDL Message into a complete

LAPD Message frame by including the necessary

header and trailer bytes (e.g., flag sequence bytes,

SAPI, CR, EA values, etc.).

• Compute the frame check sequence word (16 bit

value)

• Insert the Frame Check Sequence value into the 2

octet slot after the payload section of the Message.

• Proceed to transmit the LAPD Message Frame to

the far end terminal via the outgoing DS3 frames.

Writing a "1" to this bit-field start the transmission of

the LAPD Message Frame, via the LAPD Transmitter.

NOTE: For more information on the LAPD Transmitter,

please see Section 3.2.3.2.

Bit 2 - TxDL Busy

This Read-Only bit-field allows the local µP to poll

and determine if the LAPD Transmitter has completed

its transmission of the LAPD Message frame. This

bit-field will contain a "1", if the LAPD Transmitter is

still transmitting the LAPD Message frame to the far-

end terminal. This bit-field will toggle to "0", once the

LAPD Transmitter has completed its transmission of

the LAPD Message frame.

NOTE: For more information on the LAPD Transmitter,

please see Section 3.2.3.2.

Bit 1 - TxLAPD Interrupt Enable

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

disable the LAPD Message Frame Transmission

Complete interrupt.

Writing a "0" to this bit-field disables this interrupt.

Writing a "1" to this bit-field enables this interrupt.

Bit 0 - TxLAPD Interrupt Status

This Reset Upon Read bit-field indicates whether or

not the LAPD Message frame Transmission Complete

interrupt has occurred since the last read of this reg-

TXDS3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)

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

Not Used

TxDL Start

TxDL Busy

TxLAPD

Interrupt

Enable

TxLAPD

Interrupt

Status

R/W

RUR

0000

000

XRT7250 Datasheet(PDF) 106 Page - Exar Corporation

XRT7250 Datasheet(HTML) 106 Page - Exar Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL