METHOD AND DATA NETWORK FOR COMMUNICATING DATA CONTENT, IN PARTICULAR IN AN ELEVATOR SYSTEM

Abstract

A method and a data network for communicating data content, particularly useful in an elevator system, includes a master unit and a plurality of slave units that are connected to one another via data communication paths to exchange data telegrams having a large number of bits between one another. The master unit and the slave units are connected in series to form a chain via the data communication paths wherein a data telegram is transmitted from the master unit to a last slave unit on an outward data path. The last slave unit initiates a data return path by returning the data telegram to the master unit. The data telegram is modified by the slave units exclusively during the data return path and at least one slave unit begins to compile information requested by the master unit immediately after receiving and evaluating the data telegram.

Claims

1-14. (canceled)

15. A method for communicating data content within a data network, the data network including a master unit and a plurality of slave units being connected to one another in series to form a chain via data communication paths to exchange data telegrams between one another, the method comprising the steps of: forming a data telegram having a header, a datagram region and a checksum, the datagram region being adapted for serial storage of a plurality of datagrams, each of the datagrams including a piece of data content to be communicated and the checksum being calculated uniquely on a basis of bits in a remainder of the data telegram; the master unit transmitting the data telegram to a first slave unit of the slave units on an outward data path including all of the slave units up to a last slave unit of the slave units; each of the slave units, except for the last slave unit, receiving at a first data connection the data telegram from a direction from the master unit and forwarding via a second data connection the data telegram in a direction toward the last slave unit, and receiving at the second data connection the data telegram from a direction from the last slave unit and forwarding via the first data connection the data telegram in a direction toward the master unit; the last slave unit initiating a data return path by returning the data telegram received from the direction from the master unit at a first data connection in the direction toward the master unit via the first data connection; wherein the slave units are adapted to modify the data telegram only during the data return path; and wherein each of the slave units has a processor unit for forwarding and modifying the data telegram, at least one of the processor units being adapted to read and evaluate the data telegram on the outward data path and, when the data telegram contains a request to transmit information to the master unit on the data return path, the at least one processor unit immediately begins compiling the requested information after receiving and evaluating the request in the data telegram.

16. The method according to claim 15 wherein the data network is implemented in an elevator system.

17. The method according to claim 15 wherein the last slave unit waits for an adjustable period of time before initiating the data return path.

18. The method according to claim 15 including when one of the slave units is receiving the data telegram from the master unit or from an adjacent one of the slave units, the one slave unit forwards parts of the data telegram, while it is being received, to another adjacent slave unit or to the master unit.

19. The method according to claim 18 including checking the checksum of the data telegram, appending a supplementary datagram after a last datagram stored in the datagram region, wherein the supplementary datagram has a piece of data content to be communicated by the one slave unit, and calculating a new checksum on a basis of bits in a rest of the data telegram expanded by the supplementary datagram and appending the calculated checksum to an end of the data telegram.

20. The method according to claim 15 wherein each of the slave units independently actively starts data communication with the master unit by sending another data telegram to the master unit for this purpose, and wherein each of the slave units performs collision handling before actively starting the data communication with the master unit and sends the another data telegram only when not currently receiving and forwarding the data telegram.

21. The method according to claim 15 wherein the data communication paths formed as a twisted double line.

22. A data network for communicating data content, the data network comprising: a master unit; a plurality of slave units connected with the master unit via data communication paths for exchanging data telegrams between one another, wherein the master unit and the slave units are connected in series to form a chain via the data communication paths; wherein each of the data telegrams includes a header, a datagram region and a checksum, the datagram region being adapted for serial storage of a plurality of datagrams, each of the datagrams including a piece of data content to be communicated, and wherein the checksum is calculated uniquely on a basis of bits in a remainder of the data telegram; wherein the master unit has a master processor unit and at least one data connection and each of the slave units has an associated processor unit and first and second data connections; wherein the master unit is adapted to transmit the data telegrams via the at least one data connection to a first slave unit of the slave units on an outward data path up to a last slave unit of the slave units; wherein each of the slave units, except the last slave unit, is adapted to forward the data telegrams received at the first data connection from a direction from the master unit in a direction toward the last slave unit via the second data connection, and to forward the data telegrams received at the second data connection from a direction from the last slave unit in a direction toward the master unit via the first data connection; wherein the last slave unit is adapted to initiate a data return path by returning the data telegrams received at the first data connection from the direction from the master unit in the direction toward the master unit via the first data connection; wherein each of the slave units is adapted to modify the data telegrams exclusively during the data return path; and wherein the processor unit associated with at least one of the slave units is adapted to read and evaluate the data telegrams on the outward data path and, when any of the data telegrams contains a request to the at least one slave unit to transmit information to the master unit on the data return path, the processor unit associated with the at least one slave unit begins compiling the requested information immediately after receiving and evaluating the corresponding request.

23. The data network according to claim 22 being implemented in an elevator system wherein the master unit is connected to an elevator controller and each of the slave units is connected to an associated door switch.

24. The data network according to claim 22 wherein the last slave unit is adapted to wait for an adjustable period of time before initiating the data return path.

25. The data network according to claim 22 wherein each of the slave units is adapted to receive the data telegrams from the master unit or from an adjacent one of the slave units and to forward parts of the data telegrams being received to an adjacent one of the slave units or to the master unit.

26. The data network according to claim 25 wherein each of the slave units is adapted to check the checksum of each of the data telegrams and to append a supplementary datagram after a last stored datagram in the datagram region, wherein the supplementary datagram includes a piece of data content to be communicated by the slave unit, to calculate a new checksum on a basis of bits in a rest of the data telegram expanded by the supplementary datagram and to append the newly calculated checksum to an end of the data telegram.

27. The data network according to claim 22 wherein each of the slave units is adapted to actively start data communication with the master unit independently and to send another data telegram to the master unit, wherein each of the slave units is adapted to perform collision handling before actively starting the data communication and to then send the another data telegram only when the slave unit is currently not receiving and forwarding one of the data telegrams.

28. The data network according to claim 22 wherein the data communication paths are twisted double lines.

29. An elevator system having the data network according to claim 22.

30. The elevator system according to claim 29 comprising: a controller; an elevator car that serves several floors in a building under control of the controller; wherein the data network extends along the several floors; a security device arranged on each of the floors, the security devices being adapted to determine data content and to transmit the data content to an assigned one of the slave units of the data network; and wherein the elevator controller receives the data content from the master unit of the data network and controls a function of the elevator system based on the data content.

Description

DESCRIPTION OF THE DRAWINGS

[0077] FIG. 1 shows a data network according to an embodiment of the present invention.

[0078] FIG. 2 shows a processor unit of a slave unit of the data network from FIG. 1.

[0079] FIG. 3 shows an elevator system according to an embodiment of the present invention.

[0080] FIG. 4 illustrates a data communication method according to an embodiment of the present invention.

[0081] FIG. 5 shows an exemplary data structure of a data telegram for a data communication method according to an embodiment of the present invention.

[0082] The drawings are merely schematic and not to scale. Like reference signs refer to like or equivalent features in the various drawings.

DETAILED DESCRIPTION

[0083] FIG. 1 shows a data network 1 by means of which data content can be communicated between different subscribers in the data network 1. The data network 1 comprises a master unit 3 and a plurality of slave units 5. The master unit is denoted by “M” and the slave units are denoted by “S1,” “S2,” . . . , “Sn.” The master unit 3 and the slave units 5 are connected to one another via data communication paths 7 in the form of twisted double lines 9.

[0084] In the example shown, both the master unit 3 and each of the slave units 5 are each connected to a safety device 11 in the form of a circuit for the secure generation and/or processing of data content. In this case, the master unit 3 is connected to a safety controller 13, whereas each of the slave units 5 is connected to a safe input/output unit (Safe 10) 15. The safety devices 11 are designed in such a way that they meet increased safety requirements such as a safety integrity level SIL3.

[0085] In the example shown, the master unit 3 (M) and the slave units 5 (S1-Sn) are connected to one another in series to form a chain via the data communication paths 9. The master unit 3 has a master processor unit 17 and a data connection 19. Optionally, the master unit 3 can also have a further connection in the form of an external connection 21, via which the master unit 3 can communicate with other electronic devices, for example via an external network such as a normal Ethernet. Each of the slave units 5 has a processor unit 18, a first data connection 23 and a second data connection 25. With the exception of a first slave unit 27 (S1) and a last slave unit 29 (Sn), the first data connection 23 of a slave unit 5 and the second data connection 25 of a slave unit 5 adjacent thereto are connected to one another via one of the data communication paths 7. The first data connection 23 of the first slave unit 27 is connected to the data connection 19 of the master unit 3. The optionally available second data connection 25 of the last slave unit 29 remains unused.

[0086] According to FIG. 2, a processor unit 18 of a slave unit 5 has a microcontroller 20 which is in communication with a complex programmable logic device/CPLD 22. The CPLD 22 is arranged between two physical connections/PHYs 24, 26 and communicates with the two PHYs 24, 26. The two PHYs can be formed, for example, by a TJA1102 dual-port Ethernet PHY from NXP Semiconductors of Eindhoven, Netherlands. The CPLD 22 is configured in such a way that it forwards data substantially without delay, i.e. while the data of the same data telegram is still being received. For this purpose, the first PHY 24 is connected to the first data connection 23 and the second PHY 26 is connected to the second data connection 25 of the slave unit 5.

[0087] FIG. 3 shows an elevator system 101 in which a data network 1 is implemented. In the elevator system 101, an elevator car 103 and a counterweight 105 can be displaced vertically within an elevator shaft 109 by means of a drive machine 107 and, in the process, moved to different floors 111. The operation of the drive machine 107 is controlled by an elevator controller 113. A shaft door 115 is provided on each of the floors 111, by means of which access to the elevator shaft 109 or the elevator car 103 located behind it can be blocked or opened. A current closed state of each of these shaft doors 115 is monitored by means of a door switch 117 provided on each shaft door 115. The door switch 117 forms a safety device 11, 15 (see FIG. 1) which, depending on whether the shaft door 115 is open or closed, determines and outputs a corresponding signal or data.

[0088] In order to be able to transmit the information about the closed states of the multiple shaft doors 115 to the elevator controller 113 in a manner similar to a conventional safety chain, data communication is established between the door switches 117 and the elevator control 113 by means of the data network 1 presented herein. Each of the door switches 117 can transmit its signals or data to an assigned slave unit 5 of the data network 1 as a safety device 11. The data can then be communicated to the master unit 3 via the data network 1 and transferred therefrom to the elevator controller 113.

[0089] Possible details of the data communication to be established via the data network 1 are explained below, also with reference to FIG. 4.

[0090] In the context of data communication, data content is stored in data telegrams 31 or read out therefrom. The data telegrams 31 are composed of a large number of consecutive bits. Each data telegram 31 has a header 33 (H), a datagram region 35 and a checksum 37 (Cx). A datagram region 35 comprises one or more datagrams D.sub.1, D.sub.2, . . . , D.sub.n−1, D.sub.n.

[0091] In order to be able to establish data communication via the data network 1, the master unit 3 is configured to transfer a data telegram 31 with a header H, a datagram region 35 with a datagram Do and a checksum Co via its data connection 19 to the adjacent first slave unit 27. The datagram Do can contain, for example, instructions to one, several or all of the slave units 5. The master unit 3 thus sends the data telegram 31 via the chain-like data network 1 in the direction of an outward data path 39 to the last slave unit 29.

[0092] Each of the slave units 5, with the exception of the last slave unit 29, is configured to forward a data telegram 31 coming from a direction from the master unit 3 and received at its first data connection 23 in a direction toward the last slave unit 29 via its second data connection 25. The particular slave unit 5 forwards the data telegram 31 coming from a preceding adjacent slave unit 5 to a subsequent adjacent slave unit 5. On the outward data path 39, this forwarding takes place substantially without delay, i.e. the slave unit 5 forwards received parts of a data telegram 31 to the next adjacent slave unit 5 with as little delay as possible, i.e. preferably bit by bit, while it is still receiving other parts of the same data telegram 1. The content of the data telegram 31 is not modified by any of the slave units 5 during the outward data path 39. Accordingly, the checksum 37 in the data telegram 31 does not need to be changed during the outward data path 39.

[0093] A slave unit 5 located at the end of the chain recognizes its status as the last slave unit 29 due to the fact that it is only connected to a single adjacent slave unit 5. Accordingly, its optionally available second data connection 25 is not used.

[0094] As soon as the data message 31 originally sent by the master unit 3 reaches the last slave unit 29 (Sn), this last slave unit 29 forwards the received data message 31 via its first data connection 23 back in the direction toward the master unit 3, i.e. to the penultimate slave unit 5 (Sn−1), so that the data telegram 31 then moves along the chain in the data return path 41. The last slave unit 29 (Sn) waits, in particular after the complete receipt of the data telegram 31, for a short, adjustable period of time, for example in the range between 0.2 and 0.8 milliseconds, before it returns the data telegram 31. During the data return path 41, however, the slave units 5 (including the last slave unit 29 (Sn)) do not simply pass on the data message 31 unchanged to the next adjacent slave unit 5. Instead, each of the slave units 5 appends a piece of data content in the form of a datagram D.sub.1, D.sub.2, . . . , D.sub.n−1, D.sub.n additionally after a last previously stored datagram in the datagram region 35 of the data telegram 31. The datagram D.sub.0 sent by the master 3 is in particular overwritten. It could also be sent back to the master 3.

[0095] Since the data telegram 31 is modified each time it is forwarded from one slave unit 5 to the next slave unit 5, all slave units 5, upon receipt of the data telegram 31, also check its checksum 37 in order to be able to assess the integrity of the transmitted data. Furthermore, after each slave unit 5 has stored its data content in the form of a supplementary datagram in the datagram region 35 of the data telegram 31, it calculates a new checksum 37 based on the bits in the rest of the supplemented data telegram 31 and appends this new checksum 37 to the end of the data telegram 31. The previous checksum 37 is thus updated or replaced.

[0096] On the outward data path 39, the processor units 18 (see FIG. 1) of the slave unit 5 read the data telegram 31 and evaluate it. If the data telegram 31 contains a request to the particular slave unit 5 to transmit information to the master unit 3 on the data return path 41, the particular processor unit 18, immediately after receiving and evaluating the corresponding instruction, begins compiling the requested information and, if possible, providing it in the CPLD 22 (see FIG. 2).

[0097] FIG. 5 illustrates a data telegram 31 by way of example. Possible or optional configurations, bit lengths and contents of the data recorded in the data telegram 31 are specified in the header 33, the datagram region 35 and the checksum 37.

[0098] In principle, the data telegram 31 is structured according to the Ethernet data block format Ethernet-II in accordance with IEEE 802.3. The header 33 begins with a 7-byte long preamble, which is followed by a so-called start frame delimiter (SFD) with a length of one byte. This is followed by the destination and source MAC addresses (MAC destination, MAC source) with a length of 6 bytes each. The destination MAC address identifies the network station that is to receive the data telegram 31 and the source MAC address identifies the network station that sent the data telegram 31. This is optionally followed by what is known as a VLAN tag (802.1Q tag) having a length of 4 bytes. This is followed by a type specification (Ethertype) with a length of 2 bytes, which closes the header 33. Different types of data telegrams 31 can be distinguished on the basis of the type specification. The type specification also defines whether the data telegram 31 is transmitted in accordance with the conventional Ethernet standard or with the method described here for safety-relevant data. The header 33 is followed by the datagram region 35 (payload) of the data telegram 31, which can have a length between 46 and 1500 bytes. The data telegram 31 is terminated by the checksum (CRC32) with a length of 4 bytes.

[0099] In the example shown, the datagram region 35 is configured as a security frame 43. This is specified and identified by a special type specification not used in the conventional Ethernet standard, for example 0xEEB0. The security frame 43 begins with a data identifier (PDU) with a length of one byte. The data identifier specifies the type of data transmitted within the security frame. It thus has a comparable function for the security frame 43 as the type specification (Ethertype) for the entire data telegram 31. The data identifier is followed by version information (VERS) with a length of 5 bits. The version information indicates the version according to which the security frame 43 is constructed. The version information is followed by length information (LEN) with 11 bits. The length information specifies the length of the subsequent user data 45 (payload) of the security frame 43. This user data 45 can comprise between 43 and 1496 bytes.

[0100] The user data 45 of the security frame 43 are composed of identically structured datagrams 46 arranged one behind the other (in FIG. 4 D.sub.1-D.sub.n) with a length of 8 bytes each. The maximum length of the user data 45 of 1496 bytes results in a maximum number of 187 datagrams 46. Each datagram 46 begins with source information (SRC) one byte long, which identifies the slave unit 5 sending the datagram 46. This is followed by a one-byte-long counter (CNT) which is incremented by the slave unit 5 each time a datagram 46 is sent. It can thus be checked whether the slave unit 5 is still functioning properly. This is then followed by 4 bytes of data (DATA) which the slave unit 5 transmits in the datagram 46. The datagram 46 is concluded by a 2-byte checksum (CRC 16, cyclic redundancy check with 16 bits), which is calculated analogously to the checksum 37 of the data telegram 31 and is used to check the integrity of the datagram 46.

[0101] In the example shown, the useful data 45 of the security frame 43 include two datagrams 46 arranged one behind the other. Usually, each slave unit 5 appends a datagram 46 to the user data 45 of the security frame 43 on the data return path 41. This shows the structure of the user data 45 after the datagram 46 of the penultimate slave unit Sn−1 has been appended. The datagram 46 of the penultimate slave unit Sn−1 (datagram D.sub.n−1 in FIG. 4) follows the datagram 46 of the last slave unit Sn (datagram D.sub.n in FIG. 4).

[0102] It would also be possible for a slave unit 5 to append more than one datagram 46 to the user data 45 of the security frame 43. This could be the case if the corresponding slave unit 5 would like to transmit more than 4 bytes of data.

[0103] The data communication or the hardware components used in the data network 1 in the form of, for example, PHYs and CPLDs are in principle designed for full-duplex communication. Downward communication coming from the master unit 3 in the outward data path 39 to one or more slave units 5 can preferably be initiated exclusively by the master unit 3. During this outward data path 39, the slave units 5 pass the data telegram 31 on as quickly as possible on the fly and unchanged, but can “listen in” to its content. During the subsequent data return path 41, the slave units 5 also forward the data telegram 31 on the fly with the least possible time delay, but in doing so optionally additionally store their own data content as datagrams in the data telegram 31 as described and then also update the checksum 37.

[0104] The data communication in the direction of the data return path 41 can thus be initiated by the master unit 3 by the master unit initially sending a data telegram 31 along the outward data path 39 and the data telegram 31 then being returned from the last slave unit 29 on the data return path 41.

[0105] Alternatively, the slave units 5 themselves can spontaneously initiate data communication in the direction of the data return path 41. For this purpose, a slave unit 5 can actively output a data telegram 31 at its first data connection 23 and thus send it to the adjacent slave unit 5 on the data return path 41 to the master unit 3. However, the slave unit 5 should perform collision handling before actively starting such data communication and send a data telegram of its own accord only if no other data telegram 31 currently needs to be received and forwarded by the slave unit 5.

[0106] With the approach of data communication described herein and a data network 1 that can be used for this purpose with the described acceptable restrictions and a specialized protocol, physical connections, i.e. PHYs, which were originally developed for the Ethernet standard IEEE 802.3bw 100BASE-T1 for the automotive industry and have so far been used inexpensively, quickly and robustly for data communication over short distances in cars, can also be used for other applications.

[0107] In particular, the modifications described can allow applications in areas such as elevator systems, for example, in which data must be communicated over relatively long distances. The physical location of the 100BASE-T1 is able to combine different applications via a standard IP protocol for non-safety-critical data telegrams with the safety-critical protocol specified in this document for safety-critical data telegrams. The security-critical and non-security-critical data telegrams are distinguished on the basis of their type specification (Ethertype) in the header. The signal or the data telegram is passed through the 100BASE-T1 line, which is capable of full-duplex communication, from node to node in one direction of an outward data path and a data return path at the same time.

[0108] Finally, it should be noted that terms such as “comprising,” “having,” etc. do not preclude other elements or steps, and terms such as “a” or “an” do not preclude a plurality. Furthermore, it should be noted that features or steps that have been described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above.

[0109] In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.