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On Line Real Time Modem Testing

IP.com Disclosure Number: IPCOM000089514D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 16K

Publishing Venue

IBM

Related People

Favre, P: AUTHOR [+2]

Abstract

This paper describes a method for automatic control of modem testing, in which all maintenance and diagnostic activity in the modem subsystem is initiated and controlled by the modem subsystem. There is no dependence upon the using system.

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On Line Real Time Modem Testing

This paper describes a method for automatic control of modem testing, in which all maintenance and diagnostic activity in the modem subsystem is initiated and controlled by the modem subsystem. There is no dependence upon the using system.

The using system accesses a group of terminals via a communication adapter of some kind. The terminals are accessed by addresses sent with the data transmissions, and the data transmissions sent by the terminals are identified to the using system by terminal addresses appended by the terminals.

The fact that there is a series of modems between the communication adapter of the using system and the terminals is invisible to the using system and to the using terminals. To ensure the invisibility the modems must react to the attached terminal addresses.

In normal operating mode (run or data), neither the using system nor the terminal subsystem are aware of the existence of the modem subsystem. It would make sense, therefore, to assume that the using system is not responsible for the good operation of the modem system, especially since the using system cannot be aware of modem subsystem malfunctions during data mode.

On the other hand, means should be provided to the using system to become aware of the modem subsystem status. Whether the using system makes any use of the modem subsystem is up to the using system. It is not mandatory that the using system process the modem subsystem status word, but if the modem subsystem degrades, the using system cannot complain of the degradation.

Modem subsystem maintencance is therefore done when the modem subsystem is off-line, that is, when the using system makes the communication adapter not busy. The modem subsystem is off-line when the interface between the using system communication adapter and the primary modem is such that no data transmission has been requested or is taking place.

The only time the diagnostic programs can run is while the modem subsystem is off-line. The primary modem possesses all the initiative of the modem subsystem. The secondary modems, even though loaded with the diagnostic programs, are in a slave position with respect to the primary modem. That is to say, only the logical position of the modem determines its function. For this reason, an addressing scheme for the modems is suggested that defines primary/secondary mode. Modems can then be freely exchanged in position, which can be valuable in the event of primary modem failure.

Since it is impossible to predict how long the modem subsystem will be left in off-line mode, the diagnostic programs are fragmented so that they can be run piecemeal between data mode periods. This requirement imposes a certain structure on the diagnostic programs. Providing that the modem subsystem performance does not become too degraded, the modem subsystem will always respond to data mode demands from the using system within a certain maximum delay. This mode of response...