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XRT84L38 Datasheet, PDF (318/451 Pages) Exar Corporation – OCTAL T1/E1/J1 FRAMER
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XRT84L38
OCTAL T1/E1/J1 FRAMER
REV. 1.0.0
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When the Receive High-speed Back-plane Interface is sending the fifth payload bit of a particular channel,
instead of sending it twice, it inserts the signaling bit A of that particular channel. Similarly, the sixth pay-
load bit of a particular channels is followed by the signaling bit B of that channel; the seventh payload bit is
followed by the signaling bit C; the eighth payload bit is followed by the signaling bit D.
The following table illustrates how payload bits and signaling bits are multiplexed together into the
16.384Mbit/s data stream.
SECOND OCTET OF 16.384MBIT/S DATA STREAM
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
50
A0
60
B0
70
C0
80
D0
FOURTH OCTET OF 16.384MBIT/S DATA STREAM
BIT 0
BIT 1
BIT 2
BIT 3
51
A1
61
B1
BIT 4
71
BIT 5
C1
BIT 6
81
BIT 7
D1
SIXTH OCTET OF 16.384MBIT/S DATA STREAM
BIT 0
BIT 1
BIT 2
BIT 3
52
A2
62
B2
BIT 4
72
BIT 5
C2
BIT 6
82
BIT 7
D2
EIGHTH OCTET OF 16.384MBIT/S DATA STREAM
BIT 0
BIT 1
BIT 2
BIT 3
53
A3
63
B3
BIT 4
73
BIT 5
C3
BIT 6
83
BIT 7
D3
XY: The Xth payload bit of Channel Y
AY: The signaling bit A of Channel Y
3. After the first octets of all four channels are sent, the Receive High-speed Back-plane Interface will start
sending the second octets following the same rules of Step 1 and 2.
The Receive Single-frame Synchronization signal should pulse HIGH for two clock cycles (the last bit position
of the previous multiplexed frame and the first bit position of the next multiplexed frame) indicating frame
boundary of the multiplexed data stream. The Receive Single-frame Synchronization signal of Channel 0 puls-
es HIGH to identify the start of multiplexed data stream of Channel 0-3. The Receive Single-frame Synchroni-
zation signal of Channel 0 pulses HIGH to identify the start of multiplexed data stream of Channel 0-3. By sam-
pling the HIGH pulse of the Receive Single-frame Synchronization signal, the Receive High-speed Back-plane
Interface of the framer can identify the beginning of a multiplexed frame and can start sending payload data of
that frame.
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