Method For Determining The Topology Of A Serial Asynchronous Databus

• US 20130254443A1
• Filed: 03/05/2013
• Published: 09/26/2013
• Est. Priority Date: 03/06/2012
• Status: Active Grant

• Current Assignee: Softing AG
• Original Assignee: Softing AG
• Inventors: SIXT, Stefan
• Granted Patent: US 9,442,880 B2
• Time in Patent Office: Days
• US Class Current: 710/110
• CPC Class Codes: G06F 13/4295 using an embedded synchronisation
• CPC Class Codes: H04L 12/40078 Bus configuration home automation networks H04L12/2803; arrangements for maintenance or administration H04L41/00
• CPC Class Codes: H04L 12/40084 Bus arbitration
• CPC Class Codes: H04L 12/40136 Nodes adapting their rate to the physical link properties LAN switches H04L49/351
• CPC Class Codes: H04L 41/12 Discovery or management of network topologies

Abstract

A computer-implemented method for determining the topology of a serial asynchronous data bus, to which at least a first bus subscriber and a second bus subscriber are connected, which subscribers communicate via a prescribed bus access protocol.

Claims

1. A computer-implemented method for determining the topology of a serial asynchronous data bus, to which at least a first bus subscriber and a second bus subscriber are connected, which subscribers communicate via a prescribed bus access protocol that comprises defined request and response telegrams, the method including the steps of:

transmitting request telegrams from the first bus subscriber and receiving the request telegrams at the second bus subscriber, transmitting a respective response telegram from the second bus subscriber in response to each request telegram, and receiving the response telegrams at the first bus subscriber,

determining a plurality of time differences for the first bus subscriber between the transmission of a particular request telegram and the reception of a respective related response telegram at a first measurement site on the databus, which is associated with the first bus subscriber, wherein the first measurement site is located at the first bus subscriber, or, as viewed from the second bus subscriber, is located behind the first bus subscriber, and

calculating an average response time T_res1 that is associated with the first bus subscriber, from the plurality of differences determined for the first bus subscriber, calculating the difference between the average response time that is associated with the first bus subscriber T_res1, and an average response time that is associated with the second bus subscriber T_res2, and deriving a run time delay T_L, and thus a distance between the first bus subscriber and the second bus subscriber.

2. The method in accordance with claim 1, including the further steps of:

determining a plurality of time differences for the second bus subscriber between the reception of request telegrams and the transmission of related response telegrams at a second measurement site on the databus, which is associated with the second bus subscriber, wherein the second measurement site is located at the second bus subscriber, or, as viewed from the first bus subscriber, is located behind the second bus subscriber, and

calculating the average response time T_res2 that is associated with the second bus subscriber, from the plurality of differences determined for the second bus subscriber.

3. The method in accordance with claim 2, wherein the second measurement site is located at one end of the bus behind the last second bus subscriber.

4. The method in accordance with claim 2, wherein for purposes of determining the plurality of time differences for the first bus subscriber between the transmission of a particular request telegram and the reception of the corresponding related response telegram at the first measurement site, and for purposes of determining the plurality of time differences for the second bus subscriber between the reception of request telegrams and the transmission of related response telegrams at the second measurement site, the same measurement unit is used, which is connected in sequence at the first measurement site and the second measurement site.

5. The method in accordance with claim 4, wherein the first bus subscriber, the second bus subscriber and the measurement unit operate with their own, non-synchronised clock frequencies.

6. The method in accordance with claim 2, wherein for purposes of determining the plurality of time differences for the first bus subscriber between the transmission of a particular request telegram and the reception of the corresponding related response telegram at the first measurement site, and for purposes of determining the plurality of time differences for the second bus subscriber between the reception of request telegrams and the transmission of related response telegrams at the second measurement site, two measurement units are used.

7. The method in accordance with claim 1, wherein the average response time T_res2 that is associated with the second bus subscriber is determined in advance.

8. The method in accordance with claim 1, wherein the run time delay, T_L, between the first bus subscriber and the second bus subscriber is calculated in accordance with the following formula:

9. The method in accordance with claim 1, wherein the request telegrams and response telegrams are regular telegrams of the bus access protocol and are exchanged during regular data traffic on the databus.

10. The method in accordance with claim 1, wherein the request telegrams and response telegrams are data exchange telegrams, which are exchanged once in each input/output cycle of a bus subscriber, or are FDL status telegrams.

11. The method in accordance with claim 1, wherein the first bus subscriber is a master unit, and the second bus subscriber is a slave unit.

12. The method in accordance with claim 11, wherein

(a) the master unit transmits a request telegram to the slave unit at a transmission point in time T₀,

(b) the measurement unit at the measurement site that is associated with the master unit, receives the request telegram and at the next clock pulse edge generates a first time stamp Z_S,

(c) the slave unit receives the request telegram after a run time T_L, which is a function of the distance between the master unit and slave unit, wherein the request telegram has a length of x bit times,

(d) after reception of the request telegram is complete and a waiting time of y bit times has elapsed, the slave unit transmits a response telegram,

(e) after the run time T_L the master unit receives the response telegram at a point in time T_E,

(f) the measurement unit receives the response telegram and at its next clock pulse edge generates a second time stamp Z_E, and

(g) from the difference between the two time stamps a response time T_res, which is associated with the master unit, is determined, and

wherein the steps (a) to (g) are repeated a number of times, wherein spreading of response times which occurs as a result of variations in the waiting time of the slave unit is cancelled out by means of an average value algorithm for the calculation of an average response time T_res1 that is associated with the master unit.

13. The method in accordance with claim 12, wherein a plurality of slave units are connected to the databus, which repeatedly exchange request and response telegrams with the master unit.

14. The method in accordance with claim 13, wherein the step of determining a plurality of time differences for the master unit between the transmission of a particular request telegram and the reception of a corresponding related response telegram at the first measurement site, comprises the determination of the time differences for request and response telegram pairs, which are associated with different slave units, and

wherein the step of calculating an average response time that is associated with the first bus subscriber, comprises the calculation of an average response time for each of the slave units at the master unit.

15. The method in accordance with claim 14, wherein for each of the slave units the difference between the related average response time at the master unit and the average response time that is associated with the respective slave unit, is calculated, and the respective run time delay T_L, and thus the respective distance between the master unit and each of the slave units, is derived from the respective differences.

16. The method in accordance with claim 14, wherein from the respective run time delays T_L between the master unit and the plurality of slave units, an order is determined for the slave units along the databus, or a data bus section with a linear topology.

17. The method in accordance with claim 16, wherein if for a plurality of slave units the same or approximately the same run time delay T_L is determined, a branch-off point in the databus is detected and the following further steps are performed:

determining a plurality of time differences for a slave unit between the reception of request telegrams and the transmission of related response telegrams at a third measurement site on the databus that is associated with the slave unit, wherein the third measurement site can be located behind the branch-off point in the databus at the slave unit, or, as viewed from the master unit, behind the slave unit, and calculating of an average response time T_res2 that is associated with the slave unit, from the plurality of differences determined for the slave unit.

18. The method in accordance with claim 1, wherein the determination of the plurality of time differences for the master unit between the transmission of a particular request telegram and the reception of the corresponding related response telegram at the first measurement site, and the determination of the plurality of time differences for slave units between the reception of request telegrams and the transmission of related response telegrams at a second or third measurement site, are executed under the same or basically the same operating conditions with reference to the state and physical parameters of the databus.

19. A computer-implemented method for determining the topology of a serial asynchronous data bus, to which at least a first bus subscriber and a second bus subscriber are connected, which subscribers communicate via a prescribed bus access protocol that comprises defined request and response telegrams, wherein the first bus subscriber comprises a master unit, and the second bus subscriber comprises a slave unit, the method including the steps of

(a) the master unit transmits a request telegram to the slave unit at a transmission point in time T₀,

(b) the measurement unit at the measurement site that is associated with the master unit, receives the request telegram and at the next clock pulse edge generates a first time stamp Z_S,

(c) the slave unit receives the request telegram after a run time T_L, which is a function of the distance between the master unit and slave unit, wherein the request telegram has a length of x bit times,

(d) after reception of the request telegram is complete and a waiting time of y bit times has elapsed, the slave unit transmits a response telegram,

(e) after the run time T_L the master unit receives the response telegram at a point in time T_E,

(f) the measurement unit receives the response telegram and at its next clock pulse edge generates a second time stamp Z_E, and

(g) from the difference between the two time stamps a response time T_res, which is associated with the master unit, is determined, and

wherein the steps (a) to (g) are repeated a number of times, wherein spreading of response times which occurs as a result of variations in the waiting time of the slave unit is cancelled out by means of an average value algorithm for the calculation of an average response time T_res1 that is associated with the master unit.