Method and apparatus for interconnecting modules

1. An industrial process control apparatus comprising:

a plurality of processors and a plurality of input/output modules in which:

each processor has a unidirectional command line which is connected to a plurality of input/output modules;

each input/output module has a unidirectional response line which is connected to a plurality of processors;

each processor being arranged in operation to issue an identifier request to all of the input/output modules, and in which each input/output module is arranged in operation to respond with a response comprising a unique identifier via its response line; such that each processor is able to identify the physical location of a respective input/output module having a particular unique identifier by identifying the response line upon which said response is received; and

each response from a respective input/output module including a termination adaptor identifier that is dependent upon a type of termination and a physical location of the respective input/output module relative to the termination adaptor identifier.

2. An industrial process control apparatus according to claim 1 , in which the plurality of processors are connected together via interprocessor links.

3. An industrial process control apparatus according to claim 2 , in which the interprocessor links provide point-to-point bidirectional links between each processor and each other processor.

4. An industrial process control apparatus according to claim 2 , in which the interprocessor links communicate a broadcast signal which is received by each other processor.

5. An industrial process control apparatus according to claim 2 , in which one or more processors are directly connected to a control network and each processor has access to another control network via one of said interprocessor links and another processor.

6. An industrial process control apparatus according to claim 1 , in which each processor that is able to identify the physical location of the respective input/output module is arranged in operation to assign a logical slot number to each input/output module upon receiving said response and a logical group number to each of a plurality of said input/output modules.

7. An industrial process control apparatus according to claim 1 , in which the processors are arranged in operation to send commands to the input/output modules using low voltage differential encoding on differential command line signal pairs.

8. An industrial process control apparatus according to claim 7 , in which the differential command line signal pairs have no transmission line termination.

9. An industrial process control apparatus according to claim 1 , in which the input/output modules are arranged in operation to send responses using single ended signals.

10. An industrial process control apparatus according to claim 1 , in which, in operation signals are sent via the command lines and response lines using High-Level Data Link Control (HDLC) encoded frames of data which have been encoded using a non-return to zero inverted (NRZI) code.

11. An industrial process control apparatus according to claim 10 , in which there are a plurality of predetermined data streams which are recognised by a receiver in at least one of each of the processors and the input/output modules, each of the plurality of predetermined data streams including one or more of:

continuous ‘1’s that indicate that a respective module is absent or un-powered;

continuous ‘0’s that indicate that a respective module is powered but faulted; and

continuous 0x7E that indicate that a respective module is functional.

12. An apparatus for controlling operation of an industrial process control comprising:

a plurality of processors;

a plurality of input/output modules that are associated with a termination adaptor identifier associated with at least one of a type of termination and a physical location of the respective input/output module;

a unidirectional command line connecting each of plurality of processors to each of the plurality of input/output modules;

a unidirectional response line connecting each input/output module to each of the plurality of processors; and

each input/output module associated with a termination adapter being configured to receive an identifier request from more than one of the plurality of processors and arranged to respond to the identifier request with a response that can include the respective termination adaptor identifier via its respective response line such that each respective processor is able to identify the physical location of a respective input/output module having a particular unique identifier and the redundancy of the input/output module by identifying the response line upon which said response is received.

13. The apparatus of claim 12 further comprising a link connecting each respective processor to the other processors.

14. The apparatus of claim 13 , in which each link provides a point-to-point bidirectional connection between each processor and each other processor.

15. A method of configuring an industrial process control comprising:

connecting each of a number of processors to each of a number of signal modules with a unidirectional command line;

connecting each of the number of signal modules to each processor with a unidirectional response line;

connecting a termination assembly having a termination identity to each signal module;

assigning a logical slot number and a logical group number to each signal module upon receipt of a response on a respective unidirectional response line associated with each signal module; and

determining a redundancy and physical layout of the industrial process control based on the respective logical slot number, the respective logical group number, and the respective termination identity.

16. The method of claim 15 further comprising connecting each of the number of processors to each of the other processor.

17. The method of claim 15 wherein each processor assigns a logical slot number to each signal module upon receiving a response on a respective unidirectional response line.

18. The method of claim 17 wherein each processor sends commands to each signal module using low voltage differential encoding on differential command line signal pairs.