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PRELIMINARY
XRT79L71
100
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
However, the Transmit Section of the XRT79L71 can also be configured to externally accept values via a
certain input port and to insert this data into certain select overhead bits, within the outbound DS3 data-stream.
In this case, these "externally inserted" values for these overhead bits will overwrite that which has been
internally generated by the Transmit DS3/E3 Framer block. The XRT79L71 permits the user to implement this
overhead bit insertion by either of the following two methods.
By configuring the Transmit Section of the XRT79L71 to accept DS3 overhead data via the Transmit Payload
By configuring the Transmit Section of the XRT79L71 to accept DS3 overhead data via the Transmit
Overhead Data Input Interface (This approach will be discussed below).
FEAC bit (1)
Far-End Alarm & Control Bit
This bit carries the FEAC Message that is generated by the Transmit
FEAC Processor within the Transmit Section of the XRT79L71.
However, if the Transmit FEAC Controller block is not being used, then
these bits will each be set to "1".
FEBE bits (3)
Far-End Block Error Bits
These bits are set to [1, 1, 1] whenever the corresponding Receive DS3
Framer block detects no CP nor framing F and M bit errors within its
incoming DS3 data-stream. These bits are set to values other than [1,
1, 1] whenever the corresponding Receive DS3 Framer block detects
CP or framing bit errors within its incoming DS3 data-stream.
NOTE: These bit-fields can also be software-controlled.
TABLE 18: HOW THE TRANSMIT DS3 FRAMER BLOCK INTERNALLY GENERATES EACH OF THE OVERHEAD BITS - M23
APPLICATIONS
BIT NAME
BIT DESCRIPTION
HOW OVERHEAD BIT IS INTERNALLY GENERATED BY THE TRANSMIT DS3
FRAMER BLOCK
X-Bits (2)
FERF/Yellow Alarm Indicator
Bits
Either Software Controlled or automatically set to "0" whenever the corre-
sponding Receive DS3 Framer block declares the LOS, LOF/OOF or AIS
defect condition.
F1 Bits (14)
F-Frame Framing Alignment bits
that are of the value "1"
Set to the value of "1".
F0 Bits (14)
F-Frame Framing Alignment bits
that are of the value "0"
Set to the value of "0".
M1 Bit (1)
M-Frame Framing Alignment
bits that are of the value "1".
Set to the value of "1".
M0 Bit (2)
M-Frame Framing Alignment
bits that are of the value "0".
Set to the value of "0".
P-bits (2)
Parity Bits
Transmit DS3 Framer block computes the even parity value over the pay-
load bits within a given DS3 frame. The results of this calculation are
inserted into the two P-bit positions within the very next DS3 frame.
C-bits (21)
DS2 to DS3 Multiplexing Stuff
Indicator bits
Set to the value of "0".
TABLE 17: HOW THE TRANSMIT DS3 FRAMER BLOCK INTERNALLY GENERATES EACH OF THE OVERHEAD BITS - C-
BIT PARITY APPLICATIONS
BIT NAME
BIT DESCRIPTION
HOW OVERHEAD BIT IS INTERNALLY GENERATED BY THE TRANSMIT DS3
FRAMER BLOCK