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PRELIMINARY
XRT79L71
490
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
The very first byte of this 16-byte string is referred to as the Frame Start Marker byte. The Frame Start Marker"
byte is typically of the form [1, C6, C5, C4, C3, C2, C1, C0]. This "1" in the MSB (most significant bit) of this
first byte is used by a Receiving Terminal to identify this byte as the Frame Start Marker byte.
All of the
remaining bytes within a given Trail-Trace message will contain a "0" in their MSB. The bits C6 through C0
typically contains the results of a CRC-7 calculation that was performed over the previous 16-byte Trail-Trace
Message frame.
NOTE: The XRT79L71 will NOT compute nor insert this CRC-7 value into these bit-fields. The user will need to externally
compute the CRC-7 value over a given outbound Trail-Trace Message and through the XRT79L71 insert this CRC-
7 into these bit-fields within the Frame Start Marker byte.
The remaining 15 bytes are used for the transport of 15 ASCII characters which transport the actual Trail-Trace
message. Typically, these Trail-Trace Messages are used to transport messages that are of content/protocol
that are compliant to some of the requirements as listed in ITU-T G.831 and E.164.
NOTE: As mentioned earlier, the MSBs (most significant bits) within the each of the 15 remaining (e.g., non-Frame Start
Marker byte) MUST be set to "0".
6.2.4.2
CONFIGURING THE XRT79L71 TO TRANSMIT TRAIL-TRACE MESSAGES
The XRT79L71 contains a total of 16 Transmit Trail-Trace Message Registers, and 16 Receive Trail-Trace
Message Registers. The role of the Receive Trail-Trace Message Registers is described in SEE”RECEIVE As mentioned earlier, the XRT79L71 contains 16 Transmit Trail-Trace Message Registers (e.g., Transmit Trail-
Trace Message Register - Byte 1 through Transmit Trail-Trace Message Register - Byte 16). The purpose of
these registers is to permit the user to specify the contents of each of the 16-bytes within the outbound Trail-
Trace Message.
For Trail-Trace Message purposes, the Transmit Trail-Trace Message Controller block along with the Transmit
DS3/E3 Framer block will group 16 consecutive outbound E3 frames, into a Trail-Trace Message Super-
Frame. As the Transmit Section of the XRT79L71 is generating the very first E3 frame within this Trail-Trace
Message Super-Frame, it will read out the contents of the Transmit Trail-Trace Message Register - Byte 1, and
it will write that value into the TR byte-field, within this particular outbound E3 frame. When the Transmit
Section of the XRT79L71 is generating the second E3 frame within this Trail-Trace Message Super-Frame,
then it will read out the contents of the Transmit Trail-Trace Message Register - Byte 2 and it will write that
value into the TR byte-field, within this second outbound E3 frame. As the Transmit Section of the XRT79L71
is creating each subsequent E3 frame, within this particular Trail-Trace Message Super-Frame, it will continue
to increment to the very next Transmit Trail-Trace Message Register, read out the contents of this register, and
write this value into the TR byte-field within the current outbound E3 frame. After the Transmit Section of the
XRT79L71 has created the 16th outbound E3 frame, within this Trail-Trace Message Super-Frame (e.g., it has
read out the contents within the Transmit Trail-Trace Message Register - Byte 16 and has written this value into
the TR byte-field within this outbound E3 frame), it will begin to create and transmit a new Trail-Trace Message
Super-Frame by reading out the contents within the Transmit Trail-Trace Message Register - Byte 1 and
repeating the above-mentioned procedure.
TABLE 64: THE BYTE-FORMAT OF THE TRAIL-TRACE MESSAGE THAT THIS BEING TRANSPORTED VIA AN E3 DATA-
STREAM VIA THE TR BYTE
BYTE NUMBER
BIT 1
(MSB)
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
(LSB)
1 (FrameStart Marker)
1
CRC_Value[6:0]
2
0
TTM_Byte_1[6:0]
*
0
TTM_Byte_N[6:0]
15
0
TTM_Byte_15[6:0]
16
0
TTM_Byte_16[6:0]