XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
213
register, in order to keep the Transmit FEAC Processor
enabled.
Once this step has been completed, the Transmit
FEAC Processor will proceed to transmit the 16 bit
FEAC code via the outbound DS3 frames. This 16 bit
FEAC message will be transmitted repeatedly 10
consecutive times. Hence, this process will require a
total of 160 DS3 Frames. During this process the Tx
FEAC Busy bit (Bit 0, within the Transmit DS3 FEAC
Configuration and Status register) will be asserted, in-
dicating that the Tx FEAC Processor is currently
transmitting the FEAC Message to the remote Termi-
nal. This bit-field will toggle to "0" upon completion of
the 10th transmission of the FEAC Code Message.
The Transmit FEAC Processor will generate an inter-
rupt (if enabled) to the local μP/μC, upon completion
of the 10th transmission of the FEAC Message. The
purpose of having the Framer IC generating this inter-
rupt is to let the local μP/μC know that the Transmit
FEAC Processor is now available and ready to trans-
mit a new FEAC message. Finally, once the Transmit
FEAC Processor has completed its 10th transmission
of a FEAC Code Message it will then begin sending
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 68 presents a flow chart depicting how to use
the Transmit FEAC Processor.
N
OTE
:
For a detailed description of the Receive FEAC Pro-
cessor (within the Receive DS3 HDLC Controller block),
please see Section
4.3.3.1
.
4.2.3.2
LAP-D) processing via the Transmit DS3 HDLC
Controller
Message-Oriented Signaling (e.g.,
F
IGURE
68. A F
LOW
C
HART
DEPICTING
HOW
TO
TRANSMIT
A
FEAC M
ESSAGE
VIA
THE
FEAC T
RANSMITTER
START
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
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 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
Has
the 16-bit
FEAC Message been
transmitted to the
Remote Terminal
10 times
GENERATE THE TRANSMIT FEAC
INTERRUPT
INVOKE THE “TRANSMIT FEAC INTERRUPT
SERVICE ROUTINE.
1
1
1
1
NO
YES
NO
YES