XRT7250 datasheet(181/463 Pages) EXAR

181 / 463 page

XRT7250

DS3/E3 FRAMER IC

áç

REV. 1.1.1

162

all 1s in the FEAC bit-field of each DS3 Frame. The

Receive FEAC Processor (at the remote terminal

equipment) will interpret this all 1s message as an

Idle FEAC Message. The Transmit FEAC Processor

will continue sending all 1s in the FEAC bit field, for

an indefinite period of time, until the local µP/µC com-

mands it to transmit a new FEAC message.

Figure 61 presents a flow chart depicting how to use

the Transmit FEAC Processor.

For a detailed description of the Receive FEAC Pro-

cessor (within the Receive DS3 HDLC Controller

block), please see Section 3.3.3.1.

4.2.3.2

Message-Oriented Signaling (e.g.,

LAP-D) processing via the Transmit DS3 HDLC

Controller

The LAPD Transmitter (within the Transmit DS3

HDLC Controller Block) allows the user to transmit

path maintenance data link (PMDL) messages to the

remote terminal via the outbound DS3 Frames. In

this case the message bits are inserted into and car-

ried by the 3 DL bit fields of F-Frame #5 within each

DS3 M-frame. The on-chip LAPD transmitter sup-

ports both the 76 byte and 82 byte length message

formats, and the Framer IC allocates 88 bytes of on-

chip RAM (e.g., the Transmit LAPD Message buffer)

to store the message to be transmitted. The mes-

sage format complies with ITU-T Q.921 (LAP-D) pro-

tocol with different addresses and is presented below

in Figure 62.

FIGURE 61. A FLOW CHART DEPICTING HOW TO TRANSMIT A FEAC MESSAGE VIA THE FEAC TRANSMITTER

START

WRITE SIX-BIT “OUTBOUND” FEAC VALUE

INTO THE TxDS3 FEAC Register

This register is located at Address 0x32.

WRITE SIX-BIT “OUTBOUND” FEAC VALUE

INTO THE TxDS3 FEAC Register

This register is located at Address 0x32.

ENABLE THE TRANSMIT FEAC PROCESSOR.

This is accomplished by writing “xxxx x1xx”

into the TxDS3 FEAC Configuration & Status Register

ENABLE THE TRANSMIT FEAC PROCESSOR.

This is accomplished by writing “xxxx x1xx”

into the TxDS3 FEAC Configuration & Status Register

INITIATE TRANSMISSION OF THE “OUTBOUND”

FEAC MESSAGE.

This is accomplished by writing “xxxx xx1x” into the

TxDS3 FEAC Configuration & Status Register.

INITIATE TRANSMISSION OF THE “OUTBOUND”

FEAC MESSAGE.

This is accomplished by writing “xxxx xx1x” into the

TxDS3 FEAC Configuration & Status Register.

TRANSMIT FEAC PROCESSOR ENCAPSULATES

THE “OUTBOUND” FEAC VALUE INTO A 16 BIT

FRAMING STRUCTURE.

TRANSMIT FEAC PROCESSOR ENCAPSULATES

THE “OUTBOUND” FEAC VALUE INTO A 16 BIT

FRAMING STRUCTURE.

TRANSMIT FEAC PROCESSOR PROCEEDS TO

INSERT THE 16-BIT MESSAGE (IN A BIT-BY-BIT

MANNER) INTO THE “FEAC” BIT-FIELDS OF

EACH OUTBOUND DS3 FRAME.

TRANSMIT FEAC PROCESSOR PROCEEDS TO

INSERT THE 16-BIT MESSAGE (IN A BIT-BY-BIT

MANNER) INTO THE “FEAC” BIT-FIELDS OF

EACH OUTBOUND DS3 FRAME.

Transmission

of the 16 Bit FEAC

Message

Complete

Transmission

of the 16 Bit FEAC

Message

Complete

Has

the 16-bit

FEAC Message been

transmitted to the

Remote Terminal

10 times

Has

the 16-bit

FEAC Message been

transmitted to the

Remote Terminal

10 times

GENERATE THE TRANSMIT FEAC

INTERRUPT

GENERATE THE TRANSMIT FEAC

INTERRUPT

INVOKE THE “TRANSMIT FEAC INTERRUPT

SERVICE ROUTINE.

INVOKE THE “TRANSMIT FEAC INTERRUPT

SERVICE ROUTINE.

YES

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