MULTIPLEXER BASIC CONCEPTS

T.O. 31W2-2GSC24-2

TM 11-5805-688-14-1

NAVELEX 0967-LP-545-3011

subsequent destuffing and smoothing operations, it is

which the 23-bit stuffing code applies, and also enable

necessary to identify the multiplexer port with which the

presetting of demultiplexer minor frame and word

23 bit stuff code is associated. The 5-bit port number

counters. The 29th overhead bit conveys the sense of

information is inserted in bit positions 24 through 28 of

the data bit read from a channel card's data storage

the overhead word. Upon decoding by the demultiplexer,

the port number permits proper presetting of

performed by the multiplexer.

demultiplexer minor frame and word counters. Having

detected and decoded the first 28 bits of the overhead

5-19.

MULTIPLEXER BASIC CONCEPTS.

word, the demultiplexer is fully synchronized with the

5-20.

INTRODUCTION.

transmitting multiplexer and is informed of the type of

destuffing it must perform and the port to which the

5-21. Like most time division multiplexers, the

destuffing operation applies.

AN/GSC-24(V) design is structured about the use of

ports for the combining of applied channel inputs into a

5-17

When performing a positive stuffing operation

single interleaved serial output data stream. Simply

(indicated by the first 23 bits of the overhead word), the

stated, a port is an interval of time during which data

multiplexer issues an extra gated clock to the port

from a particular channel are allowed into the output

identified in overhead bit positions 24 through 28. The

stream. The rate at which the porting occurs is termed

clock forces a data bit from the elastic data storage

the port rate (Rp); once established for a given

indicated port is associated. Since this data bit is

multiplexer set configuration, the port rate remains

actually one bit of channel data, its sense (1 or 0) must

constant for all ports in use.

be conveyed to the demultiplexer for use in subsequent

destuffing operations. Sense of this data bit is inserted

5-22

To enable the multiplexer to simultaneously

into bit position 29 of the multiplexer's overhead word.

accept input channels of different (mixed) rates, multiple

Because no action and negative stuffing operations

ports are assigned to a single input channel. This

performed by the multiplexer do not force a data bit from

arrangement is termed port strapping. The total number

a multiplexer channel card storage register, sense of

of ports assigned to a particular channel may vary

overhead bit 29 is of no significance to the demultiplexer

between 1 and 25, and the variable is designated as K.

when the two stuffing codes are received.

The total number of ports assigned to all input channels

of a given configuration is simply the sum of all individual

5-18. In summary, a 29-bit overhead word is

channel K values, and is designated as N.

interleaved into each minor frame transmitted by the

multiplexer. The first 23 bits of the word enable initial

5-23. In addition to the total number of ports assigned

frame synchronization of the receiving demultiplexer and

to channels in a particular configuration (N), one

inform the demultiplexer of the type of stuffing action

additional port is always used within the multiplexer for

(positive, negative, or no-action) taken by the multiplexer.

the insertion of overhead data into the output bit stream.

The next five overhead bits (24-28) identify the port to

Generated internal to the multiplexer, the overhead data

include a synchronization pattern for use by the receiving

Change 1 5-5