XRT74L74
4 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
ADVANCED CONFIDENTIAL
REV. P1.1.1
224
1.
Write the 6-bit FEAC code (to be sent) into the Tx
DS3 FEAC Register.
2.
Enable the Transmit FEAC Processor.
3.
Initiate the Transmission of the FEAC Message.
Each of these steps will be described in detail below.
STEP 1 - Writing in the six bit FEAC Codeword (to
be sent)
In this step, the μP/μC writes the six bit FEAC code
word into the Tx DS3 FEAC Register. The bit format
of this register is presented below.
STEP 2 - Enabling the Transmit FEAC Processor
In order to enable the Transmit FEAC Processor
(within the Transmit DS3 HDLC Controller block) a “1”
must be written into bit 2 (Tx FEAC Enable) within the
Tx DS3 FEAC Configuration and Status Register, as
depicted below.
At this point, the Transmit FEAC Processor can be
commanded to begin transmission (See STEP 3).
STEP 3 - Initiate the Transmission of the FEAC
Message
The transmission of the FEAC code word (residing in
the Tx DS3 FEAC register) can be initiated by writing
a “1” to bit 1 (Tx FEAC Go) within the Tx DS3 FEAC
Configuration and Status register, as depicted below.
N
OTE
:
While executing this particular write operation, the
binary value “000xx110b” should be written into the Tx DS3
FEAC Configuration and Status Register. This insures that
a “1” is also being written to Bit 2 (Tx FEAC Enable) of the
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,
indicating 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
TX DS3 FEAC REGISTER (ADDRESS = 0X32)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Not Used
RO
0
TxFEAC[5]
R/W
d5
TxFEAC[4]
R/W
d4
TxFEAC[3]
R/W
d3
TxFEAC[2]
R/W
d2
TxFEAC[1]
R/W
d1
TxFEAC[0]
R/W
d0
Not Used
R0
0
TRANSMIT DS3 FEAC CONFIGURATION AND STATUS REGISTER (ADDRESS = 0X31)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Not Used
Not Used
Not Used
TxFEAC
Interrupt
Enable
R/W
x
TxFEAC
Interrupt
Status
RUR
x
TxFEAC
Enable
TxFEAC
Go
TxFEAC
Busy
RO
x
RO
x
RO
x
R/W
1
R/W
X
R0
X
TRANSMIT DS3 FEAC CONFIGURATION AND STATUS REGISTER (ADDRESS = 0X31)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Not Used
Not Used
Not Used
TxFEAC
Interrupt
Enable
R/W
x
TxFEAC
Interrupt
Status
RUR
x
TxFEAC
Enable
TxFEAC
Go
TxFEAC
Busy
RO
x
RO
x
RO
x
R/W
1
R/W
1
R0
X