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PRELIMINARY
XRT79L71
430
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
The purpose of these three (3) bit-fields is to permit a given Terminal Equipment to identify the type of payload
that is currently being transported via a given E3 data-stream. In this case, the role of these bit-fields are
somewhat analogous to that of the C2 byte (Payload Label Byte) within SONET/SDH.
The relationship
between the contents within these bit-fields and the corresponding type of data being carried via the payload
For more details on how the Transmit DS3/E3 Framer and Receive DS3/E3 Framer blocks handle the
Payload_Type[2:0] bit-fields, within the E3, ITU-T G.832 Framing format, please see SEE”SETTING THE Bits 6 and 7 - SSM Multi-Frame Indicator[1:0]
The E3, ITU-T G.832 framing format permits the user to repeatedly transmit the SSM (Synchronization Status
Message) from one terminal equipment to another. According to ITU-T G.707, the SSM is a four-bit value that
is used to identify the quality-level of synchronization/timing that the Transmitting E3 Terminal Equipment is
currently operating at. These two bit-fields, along with Bit 8 (SSM Bit) within the MA Byte are used to facilitate
the repetitive transmissions of the SSM from one terminal equipment to another.
As mentioned above, the SSM (Synchronization Status Message) is a four-bit message that is continuously
and repetitively transmitted from one terminal equipment to another, via the E3 data-stream. Bit 8 (the SSM
bit) within the MA byte is actual bit that is used to repetitively transmit the SSM from one terminal equipment to
another. Bits 6 and 7, are Multi-Frame Indicator bits that are used to identify which of the four-bits within the
SSM is currently being transmitting within Bit 8, of this particular E3 frame. Table 55 presents the relationship
between the contents of these bits (e.g., the SSM Multi-Frame Indicator bits) and the individual SSM bit that is
currently being transported via Bit 8 of the MA byte within this same E3 frame.
Bit 8 - SSM Bit
The role of this particular bit-field is described above (Bits 6 and 7 - SSM Multi-Frame Indicator[1:0])
TABLE 54: THE RELATIONSHIP BETWEEN THE CONTENTS OF THE PAYLOAD TYPE[2:0] BIT-FIELDS AND THE TYPE OF
DATA BEING TRANSPORTED VIA THE
PAYLOAD BYTES WITHIN A GIVEN E3 DATA-STREAM
PAYLOAD_TYPE[2:0]
TYPE OF DATA BEING TRANSPORTED VIA E3 PAYLOAD
000
Unequipped
001
Equipped, Non-Specific
010
ATM
011
SDH TU-12s
TABLE 55: THE RELATIONSHIP BETWEEN THE VALUES OF BITS 6 AND 7 (SSM MULTI-FRAME INDICATOR) AND THE
SSM BIT THAT IS BEING TRANSPORTED VIA BIT 8 (SSM BIT) WITHIN THE MA BYTE OF THE CURRENT E3 FRAME
BITS 6 AND 7 (SSM MULTI-FRAME INDICATOR[1:0]
SSM BIT BEING TRANSPORTED IN BIT 8 (SSM BIT) OF MA
BYTE WITHIN THE
CURRENT E3 FRAME
00
SSM Bit # 1 (The Most Significant Bit) within the SSM
01
SSM Bit # 2
10
SSM Bit # 3
11
SSM Bit # 4 (The Least Significant Bit) within the SSM