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1. FA 5 594 733 1 MULTI STATION BUS SYSTEM HAVING MEANS FOR POLLING AND UPDATING OF GLOBALLY RELEVANT INFORMATION IN PARTICULAR A STATION ADDRESS AND STATION FOR USE IN SUCH SYSTEM FIELD OF THE INVENTION The invention relates to a communication system having multiple and uniformly weighted stations that are intercon nected by a shared digital bus Such systems are in general use Uniformly weighted is understood as meaning that there is no single station present that acts as overall con troller of the bus interactions On the level of a single transfer a first station may operate as a master whereas one or more second stations would operate as slaves A subse quent transfer could then have a different master station Moreover the stations can have various different priority levels activity frequencies and hardware provisions The bus as referred to supra is metaphoric for its medium that is it may be single that is the bus at any time has only a single data value or plural channel galvanically intercon nected optical radio broadcast infrared or other The bus medium may be uniform or mixed such as a wired inter connection that has a two way station for external commu nication of infrared signals The organization may have provisions for AND ing OR ing logical states generated by the bus connected stations In other organizations such provision would be irrelevant There are various uses for this bus system i2. FOREIGN PATENT DOCUMENTS 8900717 10 1989 Netherlands OTHER PUBLICATIONS Single Chips 8 Bit Microcontrollers User Manual 1988 Philips Electronic Components and Materials Division Primary Examiner Douglas W Olms Assistant Examiner Dang Ton Attorney Agent or Firm Laurie E Gathman 57 ABSTRACT A communication system has multiple and uniformly weighted station interconnected by a shared digital bus A particular station comprises globally relevant information and with a predetermined maximum recurrence time trans mits a data packet representing such item to any other interested station If unanimous counter signalization occurs the item is in order other wise updating thereof is undertaken The unanimity is either by positive signaliza tion or by default 20 Claims 2 Drawing Sheets 12 INTERFACE CIRCUIT 4 Station U S Patent Jan 14 1997 Sheet 1 of 2 5 594 733 INTERFACE CIRCUIT INTERFACE CIRCUIT INTERFACE CIRCUIT 21 APPARATUS APPARATUS oe E G WASHING APPARATUS TELEVISION MACHINE E G DRYER DISHWASHER MONITOR TUNER J i 2 Station Station Station FIG 1 ADA KID KOO ST MO MSA SSA ACT CF ACT DB EOD ACH DB E00 ws OB 00 ACI le DCF eje DCF DCF e DF gt FIG 2A MSA SSA PsA TAa FAY Fi6 2B U S Patent Jan 14 1997 Sheet 2 of 2 5 594 733 FA
3. generator need not be extreme inasmuch as any system usually contains only a moderate number of stations say less than 50 Further as long as a unit has not gained an address definitely that is when the unit has not yet decided which address to take it may not respond to packets destined to its provisional address Now at the end of the time out the station leaves block 58 for block 51 Each station may have its own time out value or a time out value that is random ized among successive passages through block 58 Also the incrementing by 1 occurring in block 56 may be changed into a quasi randomized sequence of proposed station addresses A suitable solution is by a maximum length retrocoupled shift register because this couples the quasi randomness with the property that all addresses will be actually passed Now each unit will not try to get a unanimous counter signalization very not often A right percentage is that overall load is at most 5 On the other hand user granu larity must feel little influence of an incorrect addresses It is felt that an incorrect address should not exist for more than one minute in a home system This could mean that the time out should be a fraction of a minute Particular globally relevant informations would be the particular station s opinion of the content of other station s information cf the global real time referred to supra the wish to use a particular resource Normally the res
4. bits eight apparatuses of the same type can be distinguished The initialization Now a station address comprises a service address a type address and a follower address The service address and the type address have been assigned by the manufacturer and are programmed in the station address memory of the interface circuit Programming of the follower address is left to the user and does not take place until after the relevant apparatus has been connected to the communication bus 1 by means of the interface circuit To this end this interface circuit has an initialization program with the steps shown in FIG 3 and which is performed as soon as the apparatus is switched on More particularly the follower address FA is set to zero in a first step 50 Subsequently the start bit ST is set on the communication bus in step 51 the mode bits of the mode field MO in step 52 subsequently the station address MSA of this station is set with FA 0 in step 53 and finally the destination station address SSA of the destination station with which communication is desired is set in step 54 More particularly the destination station address SSA is made equal to the station address MSA of the master station Waiting for an acknowledge code takes place in step 55 If this code occurs in the acknowledge code field ACI so that ACTI 1 the follower address is raised by one in step 56 and the steps 51 to 55 are performed again Whenever an acknowledge code occurs A
5. respective stations could then follow respective different sequences After updating the result of the updating may be signalled to any relevant station either by repeating transmitting a data packet formatted like the original one but with the now updated information item or by effectively addressing any station present for example by adding destination default address such as zero This procedure keeps other stations abreast of any new developments Advantageously the system comprises a distinguishing device for distinguishing among actual recurrence intervals of respective ones among said stations Each station could have its own specific recurrence interval Alternatively the recurrence interval could be a time variable quantity in any relevant station The invention also relates to a station for use in such communication system Various advantageous aspects are recited in dependent claims BRIEF DESCRIPTION OF THE FIGURES For a fuller understanding of the invention reference is attached to the following description taken in connection with the accompanying drawings in which FIG 1 shows diagrammatically the general structure of a single channel communication system FIG 2a shows diagrammatically the structure of a com munication operation on an information level performed on the communication bus FIG 2b shows the structure of a station address FIG 3 shows a flow chart for assigning a station address to a sta
6. the subset should have responded to the transmission of the data packet 2 The communication system as claimed in claim 1 wherein the non unanimous counter signalization for a transmitted data packet is a response from at least one of the stations of the subset which response is different than other responses from other stations of the subset 3 The communication system as claimed in claim 1 wherein after the information is changed by said updating means the transmitting means transmits to the other stations on the digital bus a data packet representing the changed information item 4 The communication system as claimed in claim 1 wherein each station including transmitting means transmits the data packets such that the predetermined maximum recurrence intervals of each station are different and the system further includes distinguishing means for distin guishing between the predetermined maximum recurrence intervals of each station 5 A communication system as claimed in claim 1 wherein the digital bus carries at any time only a single datum 6 A communication system as claimed in claim 1 con figured as a home based system wherein a plurality of the stations are each comprised by one of a television monitor a tuner a video recorder a washing machine a drier and a dishwasher 7 A communication system as claimed in claim 1 wherein said updating means changes the information item according to a predetermined updating patte
7. CI 1 this means that another 5 594 733 5 station is connected to the communication bus which has the same service address type address and follower address as the transmitting master station If no acknowledge code is received it means that none of the other stations has a station address which corresponds to that of the master station The last used follower address FA is then stored in the station address memory in a step 57 thus ending the initialization program As described in the Reference a master station does not get access to the communication bus until a so called arbitration procedure has been formed In this arbitration procedure the mode indication bits the service address bits and type address bits and now also the follower address bits are involved The updating In a system according to the invention the stop block actually starts a particular time out after which the system again reverts to block 51 and the same procedure as for initialization ensues A particular provision not shown may be taken in case the loop of FIG 3 is cycled continuously indicating no free address is available For brevity this has not been shown in FIG 3 A few assumptions are as follows first any unit has a unique code UI or some random generator for distinguish ing itself from units of the same sort As almost any unit must contain some NVRAM already this memory may also contain such code The randomness of the randomness
8. United States Patent 5 Katoen et al OY 0 A A US005594733A 11 Patent Number 45 Date of Patent 5 594 733 Jan 14 1997 54 MULTI STATION BUS SYSTEM HAVING MEANS FOR POLLING AND UPDATING OF GLOBALLY RELEVANT INFORMATION IN PARTICULAR A STATION ADDRESS AND STATION FOR USE IN SUCH SYSTEM 75 Inventors Joost Pieter Katoen Marnix C Vlot both of Eindhoven Netherlands 73 Assignee U S Philips Corporation New York N Y 21 Appl No 943 368 22 Filed Sep 10 1992 30 Foreign Application Priority Data Sep 10 1991 EP European Pat Off 91202304 Sti Die C o a HO4L 12 403 52 USCh oeiia isisisi 370 449 370 410 370 503 58 Field of Search ou scssseeessseseenes 370 85 8 85 1 370 85 5 85 12 95 1 95 2 95 3 94 1 94 2 94 3 60 60 1 100 1 105 1 105 4 105 5 107 108 110 1 85 2 85 3 340 825 5 825 51 825 06 825 07 825 08 375 354 355 356 359 365 366 56 References Cited U S PATENT DOCUMENTS 4 387 458 6 1983 Carbrey esseererssnssnensssessresesren 370 85 12 SDAT 2 INTERFACE CIRCUIT 21 MONITOR TUNER Station INTERFACE CIRCUIT ence APPARATUS RECORDER E G WASHING APPARATUS TELEVISION MACHINE E G DRYER DISHWASHER Station 4 608 685 8 1986 Jain et al ecsesecssceetsseeseene 370 85 8 4 814 974 3 1989 Narayanan et al 370 85 2 5 177 739 1 1993 Basnuevo et al sseesseeeeees 370 85 8
9. ations each interface circuit has a memory location 23 33 43 in which a station address is stored A typical station address comprises twelve bits The structure of a communication operation on an infor mation level is shown in FIG 2A Such an operation starts with a start bit ST It is followed by a mode field MO in which three mode indication bits are transmitted They indicate the rate at which the following information will be transmitted In the master station address field MSA the 10 15 20 25 30 35 40 45 50 55 60 65 4 twelve bit master station address is transmitted from the station wishing to transmit information to a destination station The twelve bit destination station address is trans mitted in the destination station address field SSA If a station recognizes the destination address as its own address it transmits an acknowledge code in acknowledge code field ACL If this acknowledge code is not received it means that the destination station is not present or does not function or that the destination station address is received in a mutilated form No distinction is made between these three possibili ties In these cases the communication is discontinued after the acknowledge code field If the acknowledge code has effectively been received the master station transmits a control code of for example four bits in control field CF After reception of this control code the destination statio
10. herein the step of transmitting transmits a proposed address and all stations having the proposed address transmit a response and if no station transmits a response the step of detecting detects a unanimous counter signalization which indicates the pro posed address is an unused address and if a response is transmitted by a station then the steps of changing the information and the steps of transmitting the information item are repeated such that new addresses are transmitted until the step of detecting detects a unanimous counter signalization 20 The method as claimed in claim 18 wherein the steps of changing transmitting and detecting are repeated until a unanimous counter signalization is detected x F k OK
11. hich said stations are interfaced 17 A station as claimed in claim 11 wherein the updating means changes the information item according to a prede termined updating pattern 5 10 15 20 30 35 40 8 18 A method of communicating in a system having multiple and uniformly weighted stations interconnected by a shared digital bus wherein no single station acts as overall controller of bus interactions including the steps of recurrently transmitting on the digital bus a data packet representing an information item globally relevant to other stations of the system with a predetermined maximum recurrence interval between recurring trans missions of the data packet detecting counter signalizations by a subset of the other stations and changing the information item in response to a non unanimous counter signalization from the subset of other stations and wherein the counter signalization of each station is one of i a response by a station and ii no response by a station and wherein the non unani mous counter signalization for a transmitted data packet is one of i a response from less than all of the stations of the subset when all of the stations of the subset should have responded to the transmission of the data packet and ii a response from a station of the subset when none of the stations of the subset should have responded to the transmission of the data packet 19 The method as claimed in claim 18 w
12. ion and wherein the non unanimous counter signalization for a transmitted data packet is one of i a response from less than all of the stations of the subset when all of the stations of the subset should have responded to the transmission of the data packet and ii a response from a station of the subset when none of the stations of the subset should have responded to the transmission of the data packet 12 The station as claimed in claim 14 wherein the information item is a proposed address of the station trans mitting the data packet and the non unanimous counter signalization is a response from any station having an address equivalent to the proposed address 13 The station as claimed in claim 12 wherein after the information item is changed by said updating means the transmitting means transmits to the other stations a data packet representing the changed information item 14 The station as claimed in claim 11 wherein the non unanimous counter signalization is a response from at least one station of the subset but not all of the stations of the subset 15 The station as claimed in claim 11 wherein after the information item is changed by said updating means the transmitting means transmits to the other stations a data packet representing the changed information item 16 The station as claimed in claim 11 further including means for distinguishing the predetermined time intervals of each station of the communication system to w
13. n again transmits an acknowledge code in acknowledge code field ACII If this second acknowledge code is not received by the master station the communication is discontinued If the master station has received this second acknowledge code a data field DF occurs The data field may be divided into various data or command subfields each containing a data byte DB and end of data signalization EOD and acknowledge bit interval ACII Absence of the latter may trigger repeat of the most recent subfield If EOD is positive the transmission may terminate The structure of a station address is shown at FIG 2B It comprises a service address SA a type address TA and a follower address FA The service address SA comprises for example four bits and can thus distinguish sixteen services for example an audio video service a washing service a cooking baking service etcetera The type address TA com prises for example five bits so that thirty two stations can be distinguished within one service For example within the washing service a distinction can be made between a wash ing machine a drier a dish washer etcetera and within the audio video service a distinction can be made between a TV monitor a tuner a video recorder etcetera In practice the user may have a number of apparatuses of the same type for example two or more video recorders The follower address FA enables him to distinguish between these apparatuses of the same type By three
14. ncluding home based systems for audio video entertainment home environmental control lighting tem perature humidity devices for executing household chores telecommunication safety control and others A particular hazard of such a system is the low degree of organizational consistency on the level of the stations themselves as exemplified by a particular station may be temporarily deactivated because it is unplugged from the bus switched off an associated main switch by its main plug is discon nected etc Of course the bus physical transport layer should be immune against such disruption but higher protocol levels would at any rate be influenced a particular message could go astray which in particular could occur in case of an infrared or broadcast medium This could cause various levels of inconsistency in that certain stations could receive information that differs from other stations information or could even be totally absent at arbitrary instants the bus system could become con nected to another bus system Even if at each level of the separate bus system consistency would prevail such need no longer be the case on the level of the composite system SUMMARY OF THE INVENTION Amongst other things it is an object in the present invention to solve in particular but not limited to home systems the above inconsistency problems in a convenient consistent and unencumbering manner According to one of the in
15. ource itself peripheral bus transport facility is interrogated directly but the present solution allows for a more abstract or ephemeral wish without specifying the object itself We claim 1 A communication system having multiple and uni formly weighted stations interconnected by a shared digital bus wherein no single station acts as overall controller of bus interactions characterized in that a particular station comprises a transmitting means for recurrently transmitting on the digital bus a data packet representing an information item globally relevant to the other stations of the Ur 10 20 25 30 40 50 55 60 65 6 system with a predetermined maximum recurrence interval between recurring transmissions of the data packet b detecting means for detecting counter signalizations by a subset of the other stations and c updating means for changing the information item in response to a non unanimous counter signalization from the subset of other stations and wherein the counter signalization of each station is one of i a response by a station and ii no response by a station and the non unanimous counter signalization for a transmitted data packet is one of i a response from less than all of the stations of the subset when all of the stations of the subset should have responded to the transmission of the data packet and ii a response from a station of the subset when none of the stations of
16. resses should be unique and the updating would take care of making the address unique again Many things could cause two or even more stations to have the same address and the present invention would make the system stabilized again on a unique address for all stations that would observe the polling operation Another example of globally relevant information would be the value of the actual or real time The invention would keep the actual value of such globally relevant information correct even if the original station becomes temporarily disturbed and does not know which other station to address for acquiring the correct value If the original station broadcasts its own address as a destination address any other station responding thereto would mean non unanimity with respect to other stations that would keep mum This indicates that this address is already assigned to another station and the original station must choose another address In this respect the situation that all stations had the same address is considered as degenerate In practice it will not occur The updating may go according to a predetermined pat tern For an address successive incremental ions by one would be good Alternatively updating according to a pseudo random series would keep two updating stations apart from each other Especially in a start up situation where any station may start from a default address zero 5 594 733 3 this would be advantageous
17. rn 8 The communication system as claimed in claim 1 wherein the information item is a proposed address of a station 9 The communication system as claimed in claim 8 wherein the data packet contains the proposed address as a destination address and the detection means detects unani mous counter signalization as no response from any station of the subset 10 The communication system as claimed in claim 8 wherein the non unanimous counter signalization is a response from a station of the subset having an address equivalent to the proposed address 11 A station interfaceable to a communication system having multiple and uniformly weighted stations intercon nected by a shared digital bus wherein no single station present acts as overall controller of bus interactions com prising a transmitting means for recurrently transmitting on the digital bus a data packet representing an information item globally relevant to the other stations of the system with a predetermined maximum recurrence 5 594 733 7 interval between recurring transmissions of the data packet b detecting means for detecting unanimous counter from a subset of the other stations of the system and c updating means for changing the information item in response to a non unanimous counter signalization from the subset of other stations and wherein the counter signalization of each station is one of i a response by a station and ii no response by a stat
18. t the information item is correct then the original station will update or change the value of the information item there may be various physical representations of the unanimity such as by using a wired OR a one signal could in particular circumstances signal a discord or wired AND The counter signalization could be a message wherein the set of mes sages generated would indicate unanimity or otherwise In this respect all messages could indeed contain identical signalization items whereupon the original station would check the unanimity According to another solution any such message could on a suitable communication layer such as bit word or other by its occurrence alone signal lack of unanimity Furthermore the original station need not always transfer the item itself as an indirect indication abstract or other representation would suffice It is not strictly necessary that all other stations connected should actually have the facility for counter signalizing Certain stations could be slave only stations Alternatively a station may be too busy to answer and if it did not concur with the unanimity it could signal so upon the end of the next recurrence interval Various other reasons could put a par ticular station out of the relevant subset specified above According to a particular advantageous aspect of the invention the globally relevant information is an address of the particular station itself Generally such add
19. tion DESCRIPTION OF A PREFERRED EMBODIMENT General structure of the communication bus system FIG 1 shows diagrammatically a single channel commu nication bus system It comprises a communication bus 1 consisting of two data lines 11 and 12 In this case three stations 2 3 and 4 are connected to this communication bus Each station comprises an apparatus 21 31 41 which is connected to the data lines 11 and 12 by means of an interface circuit 22 32 42 Such an apparatus may be a TV monitor a video recorder an audio recorder an audio tuner a controllable set of lighting elements etcetera The com munication bus is intended to transmit control signals from a first station to a second station Some stations will act as master stations and others as slave stations Some stations will act as transmitters of data some as receivers All kinds of mixed or alternating situations are possible The commu nication operations on the communication bus which will herein be described are performed by the interface circuits A particular advantageous realization of the bus is D B c f U S Pat No 4 429 384 that is single channel twisted pair The interface circuit may be a MAB 8051 microcontroller referred to in Single Chips 8 Bit Microcontrollers User manual 1988 Philips Electronic Components and Materials Division Chapter 3 The MAB 8051 C51 52 microcontrol ler family Chapter 11 The D B specification To distinguish the different st
20. vention s aspects a particular station comprising a globally relevant information item transmits recurrently with a predetermined maximum recurrence interval a data packet representing such information item for unanimous counter signalization thereto by at least a relevant subset of actually interconnected stations thereto but upon absence of such unanimous counter signalization the particular station 20 25 45 50 55 60 65 2 initiates an updating action with respect to its own relevant information item In particular the originating station does not address the stations of the relevant subset as the originating station may not know which stations are actually present in the subset but rather it would only know that a station which should have joined in the unanimous counter signalization did not If a unanimous counter signalization is not obtained then it means that the originally transmitting station s information was outdated or otherwise erroneous Thereupon the original station begins updating The unani mous counter signalization indicates that all other stations are in unison about the original information item In this way the original station need not poll each station regarding the correctness of an information item The original station instead puts the information item on the bus and if the original station does not receive a signal which indicates that the other stations are in unanimous agreement tha
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