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Synchronization Device for Remote Multiplexing System

IP.com Disclosure Number: IPCOM000096859D
Original Publication Date: 1963-Dec-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 53K

Publishing Venue

IBM

Related People

Yhap, EF: AUTHOR [+2]

Abstract

When transmitting frames of multiplexed data between two remotely positioned stations, it is essential that frame synchronization be established and maintained between the two stations. Each station has a multiplexer and a de-multiplexer. To establish and maintain frame synchronization, each of the de-multiplexers includes a Frame Synchronization Detector. It is the function of this detector to monitor all received frame signals in order to establish whether or not the system is in frame synchronization. In order to do this, two flip flops Y and Z in the detector go through many states.

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Synchronization Device for Remote Multiplexing System

When transmitting frames of multiplexed data between two remotely positioned stations, it is essential that frame synchronization be established and maintained between the two stations. Each station has a multiplexer and a de- multiplexer. To establish and maintain frame synchronization, each of the de- multiplexers includes a Frame Synchronization Detector. It is the function of this detector to monitor all received frame signals in order to establish whether or not the system is in frame synchronization. In order to do this, two flip flops Y and Z in the detector go through many states.

the flow chart in the left drawing shows that, branching from one state to one of several others, depends on the detection of the following frame patterns: r =11000...0

r' =110XX...X

t =100XX...X

Pattern r is called the rigid frame pattern. The detection of this pattern makes it possible to establish a reference position with no ambiguity. Pattern r' consists of the first three bits of pattern r, followed by any combination of 1's and 0's. The undefined bits are represented by X's. Pattern t is called the token synchronization pattern. It consists of the three bit pattern 100 followed by data bits that can be either 1 or 0. These data bits are represented by X's.

The different states of the flip flops in the frame synchronization detector are:
Y Z: Not in frame synchronization. The M/D subsystem is entirely out of frame synchronization in this state. The detector

leaves this state only if a rigid frame pattern r is

detected. The state entered on such a detection is:

R: Rigid frame pattern detected just now, but not previously. From this state the detector can return to the bar Y bar Z

state, but only if the next frame pattern is not a rigid

frame pattern. However, if the next frame pattern is a

rigid frame pattern, the detector goes to

Y bar Z: Intermediate frame synchronization status. This state, once entered, causes the detector to be on the alert for a

t pattern, an r' pattern, or the lack of both of these

patterns, bar (r' + t). Once in Y bar Z, the detector has,

in effect, already established partial synchronization. Thus,

it need not look for the entire rigid frame pattern, r, but

only check for r', 1 1 0 X X X....X. If r' is detected, the

detector remains in the Y bar Z state. If t is detected

instead, the detector goes to state T, described later,

indicating that a t pattern has just been detected but

that the previous pattern was not such a t pattern. If

the detector fails to detect either r' and t, it goes to

Y Z: Noisy condition in establishing frame synchronization. This state represents a partial setback in the process of trying

to achieve frame synchronization. If the system is in this

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state,...