GB2432229A

GB2432229A - Communication system between two modules.

Info

Publication number: GB2432229A
Application number: GB0522860A
Authority: GB
Inventors: Matthew Stevens
Original assignee: Siemens PLC
Current assignee: Siemens PLC
Priority date: 2005-11-09
Filing date: 2005-11-09
Publication date: 2007-05-16
Anticipated expiration: 2025-11-09
Also published as: GB0522860D0; GB2432229B

Abstract

A communication system between a first module 1 and a second module 2 comprising a first line 4 between first 1 and second 2 modules used for applying a voltage by said first module 1 to said second module 2, and a second line 7 used to transmit a current from said second module 2 to first module 1, said current being dependent upon said voltage from first module 1 and the characteristics of the second module 2.

Description

Method of Communication between two modules This invention relates to a

method of communication between two modules and has a wide variety of applications. It has particular but not exclusive application to a control and a slave module, for example a control module in communication with and operating a brake on an electrical motor.

Many current electronic modules communicate in relatively complex fashion via buses which can comprise of several lines. However many modules may not require a high level of complexity in their communication. Quite often only basic information is passed between modules. In such cases current systems usually still include a basic interface comprising normally at least three connections for simultaneous, full-duplex communication i.e. data going on one line from module A to module B and data going from a second line from B to module A at the same time and a third reference line. Moreover the interfaces usually have a buffer. Current methods include transceivers having e.g. 4 wires for full duplex communication. In many applications even such limited complexity increases cost unnecessarily.

In some cases also, a control unit may be in communication with several different types of slave units and a reasonable amount of data is passed between them. For example the control unit may wish to know which slave unit it is communication with. In such examples data communication is sent digitally, e.g by means of data frames. The frames usually include a header identifying each module; such systems thus often require even basic protocol.

The invention overcomes the complexity and cost for many systems.

The invention comprises a communication system between a first module and a second module comprising a first line between first and second modules used for applying a voltage by said first module A to said second module B, and a second line used to transmit a current from said second module B to first module A, said current is dependent upon said voltage from first module A and the characteristics of the second module B. Further, the second line between said module A and said module B acts as the reference line for the transmitted voltage.

The characteristics of module B includes operational or fixed characteristics e.g. line breakage, operating level, operating mode, device type.

The second module B has means to read and interpret said voltage as control or test data.

Figure 1 shows a simple embodiment of the invention comprising a module 1 in communication with second module 2. Module 1 includes circuitry (a voltage transmitter 3') to transmit a voltage signal across line 4' with respect to line 7' to a voltage read circuit 5' in module 2' which also includes a current source 6'. A current signal is sent down a second wire 7' back to module 1 where it is measured by a current read circuit 8'. The first module may be a control module and the second may be a slave module such as a brake on an electric motor.

In an even simpler embodiment of the invention the voltage read circuit may be eliminated. In any case the two wires (or lines) alone allow information to be passed between the modules.

Figures 2a and 2b shows an embodiment of the figure 1 example. In figure 2a, the voltage transmitter's voltage read circuit current read circuit and current source are shown by broken lines and have the same reference numerals as in figure 1. The control module 1 has a voltage output circuit which allows two output levels, a high and low voltage level. Figure 2b is a simplified representation of the circuit of figure 2a. Module I has two voltage sources lOa and I Ob for the high and low level respectively the module 2 has two 5mA current sources 9a and 9b (one hard wired and the other switchable). In this particular example, the current output on line to module 1 is 5ma, if switch 11 is open; if this switch is closed the output on line to module a will be lOmA (5mA + 5mA). Thus in this example there are two voltage levels which can be output to module 2, thus allowing choice of two modes of operation.

In figures 2a and 2b are also shown a voltage read circuit 5. This circuit is optional and allows module 2 to operate according to the voltage level seen across the input lines.

Thus module 1 can detect whether switch is open, and it would be readily understood by a person skilled in the art that if the switch connection was to implement different functionality of the module 2, then module 1 can obtain information about a range of operating characteristics of module 2, e.g. which operating mode it is currently functioning, what the power lever is, etc. Furthermore if there was zero current fed back to module 1 whilst the voltage to module 2 was positive, this would be indicative of a fault.

Although the voltage source and read circuit are shown as blocks they may in practice be very basic circuitry.

In a comprehensive embodiment, module 2 can (additionally to receiving a voltage from module 1) also adjust/toggle different levels of current feedback on top of that nominally transmitted such that module 1 can read data sent by module 2. In this way both modules can interrogate and obtain useful information about each other.

In all the examples so far we have talked about two modules. The invention is not limited to two modules but encompasses examples where there are many module connected to each other. A common set up of such a system is a master (control) module and a number of subordinate modules each performing different tasks. They may all use a common voltage line and current line.

The advantage of the invention is that between modules there is a minimal wire interface, just two wires between modules. There is simple detection interpretation e.g. no current feedback means effectively no module present i.e. wire break. Module recognition is simple; recognition of a particular module by detecting a different level dependent on the module characteristics. Simple circuitry only is required with no or little software is required, just simple circuitry. The invention is also flexible in that the user implements the design with the voltage and current levels as they see fit without the restriction of the component that conventionally would be

necessary in prior art systems.

Claims

Claims 1. A communication system between a first module and a second

module comprising a first line between first and second modules used for applying a voltage by said first module to said second module, and a second line used to transmit a current from said second module to first module, said current being dependent upon said voltage from first module and the characteristics of the second module.

2. A system as claimed in claim 1 wherein the said characteristics of the second module include operational or fixed characteristics.

3. A system as claimed in claim 2 wherein the characteristics include any one: lines breakage, operating level, operating mode, or device type.

4. A system as claimed in claims 1 to 3 wherein said second module has means to read and interpret said voltage as data 5. A system as claimed in claim 4 wherein the operation or control of said second module is dependent upon said voltage.

6. A system as claimed in claim 5 wherein the operating mode or level of said second module is dependent on the voltage input from module one.

7. A system as claimed in any preceding claim wherein there are no other lines between the modules.

8. A method to communicate between a first module and a second module comprising applying a voltage by said first module on a first line between first and second modules and transmitting a current along a second line said second module to first module, said current being dependent upon said voltage from first module and the characteristics of the second module 9. A method claimed in claim 8 wherein the characteristics of module includes operational or fixed characteristics.

10. A method as claimed in claim 8 or 9 wherein the characteristics include any one of the lines breakage, operating level, operating mode, device type.

12. A method as claimed in claims 8, 9, or 10 wherein said second module is controlled by said first module, dependent upon said voltage.