The invention concerns a communication system of a modular telecommunications system, in which the various operational units, i.e. modules, of the telecom¬ munications system are connected together in a network by means of a serial bus in order to provide for com¬ munication between the different parts of the system. Generally speaking, the invention relates to telecommunications systems which typically comprises a plurality of transmission units managing and intercon¬ necting various devices, such as telephones, exchanges, computers and other sources providing digital signals, with each other and/or with desired transmission lines.

Whenmulti-module telecommunication systems are designed, there is an obvious need to interconnect the various modules. This is usually implemented by using at least one bus, or a so-called backplane bus, which runs in a subrack from one module board to another and by which the boards in the subrack can communicate with one another.

In known systems, like the SDH and PDH trans¬ mission networks, the buses cannot extend as such from one subrack implementing the telecommunications system to another. In larger systems, data communication with the physically remotest modules is usually implemented by a high speed serial interface. For communication e.g. between different parts of a system, the backplane buses of different arrangements usually have to be converted to be suitable for a serial interface. In addition, debugging is usually implemented in the modules either by testing every module, or board, separately or by using an asynchronous debug interface provided on the board, whereby the operation of the processor of said

board can be monitored by a terminal. Implemented in this manner, detection of errors in software or hardware in a large multi-module telecommunications system is naturally a very time-consuming and complicated operati- on, since the modules must always be monitored and de¬ bugged separately, either in a test device or via their own debug ports. There are no system debuggers, and thus also no remote debugging possibility.

The aim of the instant invention is to provide a method of forming a new kind of communication channel between the modules of multi-module telecommunications systems. The system according to the invention is cha¬ racterised in that the serial bus is configured to make each of the modules addressable for read and/or write operations on different hardware and program levels recognized by the serial bus, said levels including network management, network module and system develop¬ ment and maintenance levels, in order to effect at least network management, network module intercommunication, system testing and debugging by means of a terminal equipment connected to the system.

The advantages of the invention include a di¬ rect link between modules without bus conversion, a direct monitoring and debug interface to all modules from one terminal, a remote use possibility, easy expan¬ dability, and a possibility of using network or LAN technology according to the standards in the implementa¬ tion of communication. The potential of the system ex¬ pandability is recognized by e.g. the fact that as each module is connected to the system via only one interfa¬ ce, it means that the modules may be physically located and connected freely within the system.

The invention is thus based on utilization of a serial bus as a multi-level channel, in which diffe- rent operations - such as transmission of data, network

management, maintenance and development of the system - are performed on each level.

Other advantageous embodiments of the invention are characterised by what is disclosed in the attached claims.

In the following the invention will be descri¬ bed by means of one embodiment with reference to the attached drawings.

Fig. 1 shows a generalized physical architectu- re for a telecommunications management network,

Fig. 2 shows interconnection of different modu¬ les of a telecommunications system by the arrangement according to the invention.

In figure 1, a generalized physical architectu- re for a telecommunications management network is shown. The management network, which corresponds to the CCITT M.30 recommendation, consists of an operations system OS, a data communication network DCN, a mediation device MD, and a local communication network LCN. Between the different parts of the management network, as well aε between the network and the network elements NE and the workstations WS of the telecommunications system, diffe¬ rent interfaces, like the F interface and the Q1..Q3 in¬ terfaces are used. Some of the interfaces, like the F interface, generally used for network management on the highest level, are rather freely defined non-standard interfaces, which implementation is decided by the manu¬ facturer. Other interfaces, like the CCITT interconnec¬ tion protocol interface Q3, may be fully specified and thus manufacturer-independent. Figure 1 shows the varie¬ ty of interfaces and connections, which in the prior art are neccessary to interconnect the various modules of a system.

Figure 2 shows two pieces of equipment 1, 2 with eight modules (circuit boards) each. Each equipment

typically comprises a frame structure into which boards are inserted and which has contactors for the pins of the boards for connecting the module, or board, to the system. According to the invention, the modules of each equipment and the equipments 1, 2 themselves are inter¬ connected by one serial bus 3, such as an Ethernet LAN network. A coaxial Ethernet link is used between the pieces of equipment and for connecting a workstation 4 to the system. It essential to notice, that according to the present invention only one physical interface is needed for each module, i.e. the same interface can be used for network management, network module intercommunication, for monitoring the operation of the modules, for system development, information maintenance and operation tes¬ ting on module and system levels, and for debugging both on source code and register control levels. All these operations can be carried out, without having, for exam¬ ple, different F and Q1...Q3 interfaces (see figure 1) and buses, either by a local workstation or from a dis¬ tance e.g. via a telephone cable or some other cable. By network module intercommunication is meant, for ex¬ ample, communication between modules assigned for the same task, and communication between modules constitu- ting a higher level equipment consisting of several dedicated modules (see figure 2) .

By way of example, three windows are shown on the display of the workstation, two modules and the net¬ work being simultaneously analyzed in the windows. In module debugging, a debug interface integrated in the module is used, which enables direct monitoring and control of the operations of the processor of the board. A debug program of the operating system, debug and dis¬ assembler programs of the source language may be used as tools. It is known to one skilled in the art how to

work in such an environment, by connecting on the site a debug terminal to one module after another.

In the arrangement according to the invention, the same LAN link that is provided for intermodular communication is also used for module debugging. The system is an open system when all modules are connected directly to the network and the network is used for all intermodular communication.

A plurality of modules can be monitored and debugged concurrently over the same link, by connecting workstations directly to the network. Detection of er¬ rors, analysing, updating and eliminating of errors in software can thus be performed without interrupting the normal operation of the modules. The system according to the invention also provides a possibility of trans¬ ferring and/or copying software e.g. when the system is developed or updated.

A network analyzer or a debug program can be used for examining and debugging the network. This also provides an interface for testing the overall operation of the system.

The monitoring/debug interface can be connected from the network to a telecommunications line, over which remote operation can be performed. When a workstation provided with suitable soft¬ ware in connected to the network, a plurality of debug tools becomes available, varying from network analysis to examination of a memory location in a certain module. Debugging can be carried out on various levels in a fully integrated manner. The different levels may be defined e.g. in the following manner.

- Network management by a LAN-like analyzer/ debugger. The analyzer is used for examining data sent by different units (holders of network addresses) of the network for checking e.g. errors. The analyzer may be

a separate tool that is run by a workstation concurrent¬ ly with but separately from the other debug tools, or it may be integrated into the debug level used (network management level) . - Assigning of a network module for detection of errors on a system level. Messages and processes can then be monitored by the debugger of the operating sys¬ tem of the module (network module level) .

- Possibility of examining the source code by a source language debugger (source code level) .

- Possibility of low level debugging by a dis¬ assembler, and of examining the memory, etc. (register level) .

- Possibility of using any combination of debug tools for one or more modules.

It is obvious to one skilled in the art that the embodiments of the invention are not limited to the one embodiment described above but that they may vary within the scope of the attached claims.