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Maxim > Design Support > Technical Documents > Application Notes > T/E Carrier and Packetized > APP 345
Keywords: T1, framer, SCT, single chip transceiver, AT&T, SLC96, SLC-96, TR-08, T1 framers
APPLICATION NOTE 345
DS21352/552, DS2151, DS2152, DS2141A,
DS21Q42 Programming SLC-96
May 31, 2001
Abstract: This application note describes how to use the SLC-96 mode found in all Dallas Semiconductor
T1 framers and single chip transceivers (SCTs). The SLC-96 mode is used in T1 was designed by AT&T
as a digital loop carrier system that provides service for 96 subscribers over 3 to 5 separate T1 lines.
The frame format of SLC-96 closely resembles that of the super frame (SF or D4) format but additional
data link information is transferred to make advanced functions such as single party, multiparty, coin
telephone, and special service circuits available. Because of the complexity of the SLC-96 specification,
special synchronization circuitry, data registers, and status registers were added to the T1 devices which
allow the designer to take advantage of the SLC-96 functionality. The application note goes into an in-
depth explanation of how the SLC-96 circuitry operates and explains the how the data link transports the
additional C, M, A, and S bit information. The C, M, A, and S bits stand for the concentrator field,
maintenance field, alarm field, and protection line switch field respectively. Together these bits are used
to create the SLC-96 data link. To assist in the software design, flow charts are included with step-by-
step instructions for transmitting and receiving data over the SLC-96 data link. In the end, the designer
should have enough information to implement the necessary SLC-96 communications in the target
system.
Introduction
This application note applies to the following products:
T1 Framers T1 SCTs
DS2141A DS2151
DS21Q41B DS2152
DS21Q42 DS21352
DS21FF42 DS21552
DS21FT42 DS21Q352
DS21Q552
In a SLC-96-based transmission scheme, the standard Fs-bit pattern is robbed to make room for a set
of message fields. The SLC-96 multiframe is made up of six D4 superframes, so it is 72 frames long. In
the 72-frame SLC-96 multiframe, 36 of the framing bits are the normal Ft pattern and the other 36 bits
are divided into alarm, maintenance, spoiler, and concentrator bits, as well as 12 bits of the normal Fs
pattern. Please see the Bellcore document TR-TSY-000008 for more details about SLC-96.
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