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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
193
6.4.4.1.2
If the Transmit DS3 Framer is operating in C-bit Parity
Frame Format then the FEAC bit-field of the DS3
Frame can be used to transmit the FEAC messages
The Transmit FEAC Processor
(See Figure 51). The FEAC code word is a 6-bit val-
ue which is encapsulated by 10 framing bits, forming
a 16-bit FEAC message of the form:
where ‘xxxxxx’ is the FEAC code word. The rightmost
bit (e.g., a “1”) of the FEAC Message, is transmitted
first. Since each DS3 frame contains only 1 FEAC bit,
16 DS3 Frames are required to transmit the 16 bit
FEAC Code Message.
The Overhead Generator contains two registers that
support FEAC Message Transmission.
Tx DS3 FEAC Register (Address = 1Dh)
Tx DS3 FEAC Configuration and Status Register
(Address = 1Ch)
Operating the Transmit FEAC Processor
In order to transmit a FEAC message to the “Far-End”
Receiver, the user must execute the following steps.
1.
Write the 6-bit FEAC code (to be sent) into the
Tx DS3 FEAC Register.
Enable the Transmit FEAC Processor.
Initiate the Transmission of the FEAC Message.
2.
3.
Each of these procedures will be described in detail
below.
Writing in the FEAC Codeword
In this step, the local μP/μC writes the six bit FEAC
code word into the Tx DS3 FEAC Register. The bit
format of this register is presented below.
Enabling the Transmit FEAC Processor
In order to enable the Transmit FEAC Processor the
user must write a “1” to bit 2 of the Tx DS3 FEAC
Configuration and Status Register, as depicted below.
Tx DS3 F-Bit Mask3 Register, Address = 1Ah
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
FBit Mask
(15)
FBit Mask
(14)
FBit Mask
(13)
FBit Mask
(12)
FBit Mask
(11)
FBit Mask
(10)
FBit Mask
(9)
FBit Mask
(8)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Tx DS3 F-Bit Mask4 Register, Address = 1Bh
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
FBit Mask
(7)
FBit Mask
(6)
FBit Mask
(5)
FBit Mask
(4)
FBit Mask
(3)
FBit Mask
(2)
FBit Mask
(1)
FBit Mask
(0)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
X
X
X
X
X
X
0
1
1
1
1
1
1
1
1
Tx DS3 FEAC Register—Address: 1Dh
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
TxFEAC [5]
TxFEAC [4]
TxFEAC [3]
TxFEAC [2]
TxFEAC [1]
TxFEAC [0]
Not Used
R/O
R/W
R/W
R/W
R/W
R/W
R/W
R/O