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FOUR CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L54
PRELIMINARY
REV. P1.1.2
180
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 P/C 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
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.
Is
Transmission
of the 16 Bit FEAC
Message
Complete
?
Is
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.
1
NO
YES
NO
YES