Browse Prior Art Database

Data Transmission Procedure Detection

IP.com Disclosure Number: IPCOM000046419D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Cholat-Namy, J: AUTHOR

Abstract

This system enables the detection of a modification in data transmission mode, e.g., switching from BSC (binary synchronous communication) to SDLC (synchronous data link control), with a minimum amount of hardware and software.

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Data Transmission Procedure Detection

This system enables the detection of a modification in data transmission mode, e.g., switching from BSC (binary synchronous communication) to SDLC (synchronous data link control), with a minimum amount of hardware and software.

The hardware (Fig. 1) includes two shift registers (one (register 10) being one byte long and the other (register O) two bytes long), a converter (CONV) for converting NRZI coded bit stream into NRZ coded bit stream and compare means (not shown) for comparing the contents of the registers to specific coded bit streams in order to analyze the received message. The analysis is performed according to the algorithm of Fig. 2.

As shown in Fig. 2, the contents of register 10 are compared with the SDLC flag byte, i.e., the hexadecimal value "7E". If a "7E" is identified in the bit stream, the chances are that the received message is in SDLC. The contents of register 10 are again checked for the next bytes. A repetition of 7E contents implies that SDLC is effectively the transmission mode being used; then the next byte should be an Address byte which may be stored for further processing when needed. The algorithm then proceeds, looking for an end of message indication within register 10 whose contents D would thus be either a flag 7E or a continuous string of ones or, in other words, a byte the hexadecimal value of which would be FF.

Now, assuming the initial test of register 10 contents resulted in a negative answer, then the tests would be switched to the contents of at least portions of register 0. If the b...