Method for Sensing Input Signal Changes

• US 20120131373A1
• Filed: 11/23/2011
• Published: 05/24/2012
• Est. Priority Date: 11/23/2010
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Röhle, Holger, Simon, Matthias
• Granted Patent: US 8,775,852 B2
• Time in Patent Office: Days
• US Class Current: 713/400
• CPC Class Codes: G05B 19/0423 Input/output
• CPC Class Codes: G05B 19/054 Input/output

Abstract

A method for sensing input signal changes at an input of an input/output module operated in an automation system in which a signal is sampled by an input/output module. A change event and a timestamp associated with the change event are generated when a change in the sampled signal occurs and a value pair comprising the change event and the timestamp is stored in a higher-ranking automation component to the input/output module. The input/output module and the higher-ranking automation component are operated clock-synchronously with respect to one another by a clock pulse, and the timestamp is calculated centrally on the higher-ranking automation component based on the clock-synchronous operation.

Claims

1. A method for sensing input signal changes at an input of an input/output module operated in an automation system, comprising:

sampling a signal by the input/output module and generating a change event and a timestamp associated with the change event when a change in the signal occurs;

storing a value pair comprising the change event and the timestamp in a higher-ranking automation component having a higher ranking than the input/output module; and

operating the input/output module and the higher-ranking automation component clock-synchronously with respect to one another by a clock pulse, the timestamp being calculated centrally on the higher-ranking automation component based on the clock-synchronous operation.

2. The method as claimed in claim 1, wherein the timestamp is generated by addition of an instantaneous time at a time instant of the clock pulse and a multiple of a sampling interval of the input/output module.

3. The method as claimed in claim 2, wherein the signal is sampled in the input/output module at a frequency resulting from a division of a clock period of the clock pulse by the sampling interval.

4. The method as claimed in claim 3, further comprising:

buffering a number of sampled values corresponding to the frequency in the input/output module and transmitting the number of sampled values to the higher-ranking automation component; and

performing a check in the higher-ranking automation component based on a series of values to determine a value at which the signal change occurred,

wherein a position of the value at which the signal change occurred within the series yields a multiple used for calculating the timestamp.

5. The method as claimed in claim 3, further comprising:

buffering a number of sampled values corresponding to the frequency in the input/output module; and

performing a check in the input/output module based on a series of values to determine a value at which the signal change occurred;

wherein a position of the value at which the signal change occurred within the series yields a multiple used for calculating the timestamp, said multiple being transmitted to the higher-ranking automation component.

6. The method as claimed in claim 3, further comprising:

operating an edge detector in the input/output module to detect when the signal change occurs; and

incrementing a counter in the input/output module for each value sampled;

wherein a count of the counter yields a multiple used for calculating the timestamp when an edge is detected by the edge detector and said multiple being transmitted to the higher-ranking automation component.

7. The method as claimed in claim 6, wherein the edge detection is performed in an analog manner in the input/output module, a smaller sampling interval being chosen by the analog edge detection and a degree of precision of the timestamp calculation being improved.

8. The method as claimed in claim 2, further comprising:

operating a clock in the higher-ranking automation component to provides the instantaneous time, said clock being synchronized with other automation components in the automation system.

9. The method as claimed in one of claim 1, wherein the higher-ranking automation component is operated as an interface module and the input/output module sends acquired values to the interface module over a peripheral bus, the interface module in turn being operated on a fieldbus connected to an automation device.