D2B device station address initialization starting with stored a

Details D2B device station address initialization starting with stored a D2B device station address initialization starting with stored a

1995-01-25

1998-01-27

Chin, Wellington

Multiplex communications

Channel assignment techniques

Polling

370457, 370489, 395281, 39542101, H04L 12403

Patent

active

057128529

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a single channel communication bus system. The system includes a communication bus having a plurality of stations connected to it. The stations can communicate with one another via the communication bus. Each station has a unique station address assigned. The stations include an interface circuit which is adapted to call any destination station by generating a destination station address of said destination station. The interface circuit is also adapted to receive an acknowledge signal which is transmitted by the relevant destination station if the station address of said destination station corresponds to the transmitted destination station address. The interface circuit of a station is further adapted to perform an initialisation program under the control of which the interface circuit is able to generate and transmit a plurality of different destination station addresses in a determined sequence. Such generation and transmission are discontinued upon absence of an acknowledge signal. The destination station address that is the last that has been generated and transmitted is assigned as the master station address to said station.
Such a single channel communication bus system is known from the Dutch patent application No. 8900717 which has been published on Oct. 16, 1990. In said patent application has been described how a new device or station is added to the bus system. When the station has been switched on, a software protocol in said station will initialize the procedure to find a unique address for said station. The station address initialisation involves in fact two steps. A first one is choosing an address and the second one is verifying whether that address is unique. In order to find out whether said address is unique, the added station sends a chosen address on the bus to all other stations which are connected to the bus system. Each station which has already been active in the bus system checks whether the address sent by the newly added station corresponds with its own address or not. In the first situation the station that identifies the address sent by the newly added device as its own, will send back to the newly added station an acknowledge signal. So, if the newly added station receives an acknowledge signal it can verify that the address chosen by it previously is not unique. As a result in a second cycle the newly added station will choose another address different from the first chosen one and the protocol as described hereinbefore is repeated up to the moment where no acknowledge signal will be received by the newly added station. This means that there is no station having this address chosen by the newly added station and thus this address is unique. As soon as this situation occurs the newly added station will adopt this unique address as its own.
The above described station address initialisation can be used in a D2B system, which for instance has been described in U.S. Pat. No. 4,429,384. From the description of the D2B system in this U.S. Pat. No. 4,429,384 can be deduced that the D2B should perform in a reliable way in a low cost and possible noisy environment. Experience has shown that signals on buses sometimes deteriorate which as a consequence means that the above initialisation procedure can be ruined. Some station on the bus system may sent an acknowledge signal to inform the newly added station that the address send by it is not unique, but if such acknowledge signal is deteriorated then the newly added station will adopt said address as its own, but said address is not unique. As a result communication between these two stations and other stations will be disastrous, because if one of the two stations is addressed by another station both stations will respond and mostly in different ways because each station might be a totally difference type of device. Also in this case no proper initialisation will take place.
Further the Dutch patent application 8900717 discloses that the message including the destination address also comprises the address of

REFERENCES:
patent: 4429384 (1984-01-01), Kaplinsky
patent: 4661902 (1987-04-01), Hochsprung et al.
patent: 5150464 (1992-09-01), Sidhu et al.
MAB 5051--Single Chip Microcontrollers; User Manual 1988, Philips Electronic Components and Materials, Chapters 3 and 11.

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