Patent Publication Number: US-2010125344-A1

Title: Central subassembly for a flexible expandable automation device

Description:
Priority is claimed to German Application No. DE 10 2008 058 061.9, filed on Nov. 18, 2008, the entire disclosure of which is incorporated by reference herein. 
     The invention relates to a central subassembly for a flexible expandable automation device. 
     BACKGROUND 
     Commercially available expandable automation devices (also known as programmable logic controllers) or expandable automation devices described in patent documents can be adapted to a wide variety of automation tasks and are used, in particular, in the field of industrial automation technology and in the field of switching and control technology. 
     Automation devices are usually constructed in modular form from a central subassembly, communication couplers and expansion modules such as external input/output devices. The central subassembly according to the known prior art comprises different subassemblies such as a central processing unit (also referred to as a CPU), a voltage supply and an interface for connecting external input and output modules. The external input/output modules are electrically connected to the central subassembly via an internal bus connection in the form of an input/output bus. 
     At present, non-volatile storage of remanent data, that is to say program variables, for example of an operating system or an application program, is based on static data storage modules which are supplied with a supply voltage from an energy store (battery, capacitor or rechargeable battery) when the automation device is switched off and can therefore retain the values of the variables. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides specifying a central subassembly for a flexible expandable automation device in which non-volatile storage of data, in particular variables of an application program, is ensured independently of an energy store in the central subassembly and the computation power of the CPU in the central subassembly is reduced. 
     The central subassembly according to the invention can be expanded with at least one external expansion module which can be connected via an input/output bus and is preferably in the form of an external input/output module. An interface for connecting the external input/output module, a first electronic subassembly having a central processing unit in the form of a microcontroller, a second electronic subassembly having inputs and outputs for connecting the central subassembly to a process, and a third electronic subassembly for supplying voltage to the central subassembly are arranged in the housing of the central subassembly. 
     The first electronic subassembly in the central subassembly has a first microcontroller, a volatile memory for storing data, for example of an operating system, an application program and variables of the application program, during operation of the central subassembly, and a flash memory for non-volatile buffering of the data stored in the volatile memory. At least one application program and an operating system (also referred to as firmware) are respectively stored in the memories. 
     The data transmitted to the flash memory from the volatile memory are referred to as remanent data below since they are retained in the flash memory in the event of a voltage failure in the central subassembly. 
     If the central subassembly of the automation device is in the operating state, the remanent data are stored in the volatile memory and are used by the application program in the memory. The application program is executed by the first microcontroller. 
     According to the invention, a first function which stores the remanent data in the flash memory when the voltage supply for the central subassembly fails is integrated in the application program. 
     A second function which copies the data which have been previously stored in the flash memory to the volatile memory again when the voltage returns using the second function is also integrated in the application program. 
     Data are interchanged between the volatile memory and the flash memory by the first microcontroller using an internal address/data control bus. 
     The use of the flash memory for intermediate storage of the data thus advantageously ensures non-volatile storage of the data, preferably the application program variables, of the central subassembly of the automation device. 
     In one refinement of the central subassembly according to the invention, a second cost-effective microcontroller is provided, as a preprocessor, in the second electronic subassembly in the central subassembly, which microcontroller is connected to the inputs and outputs arranged on the second electronic subassembly and controls and evaluates the process voltages, switching and/or control signals from the process which are applied to the inputs and outputs as well as the signals output from the first microcontroller (also referred to as process signals below) for the first microcontroller. The process signals are preprocessed using programs stored in the second microcontroller. 
     Examples of preprocessing functions are:
         input filtering for digital input signals with a time constant which can be parameterized,   implementation of analogue value measurements,   implementation of analogue value outputs,   counter functions, for example counting up/down, or incremental signals as a fast counter function, and   provision of a digital output with a periodic square-wave signal with an adjustable pulse width.       

     The second microcontroller which is in the central subassembly according to the invention and is used as a preprocessor advantageously makes it possible to reduce the computation power of the first central microcontroller in the central subassembly of the automation device. 
     In addition, as a result of the fact that a fast counter function is integrated in the second microcontroller, the computation power of the first microcontroller is likewise not taken up for this function. 
     One advantageous refinement of the central subassembly according to the invention provides for the hardware structure of the second microcontroller to be partially used, for example by means of a digital converter integrated in the second microcontroller, to implement analogue value measurements and analogue value outputs without taking up the computation power of the first microcontroller. 
     In one particular refinement of the central subassembly, the second microcontroller in the central subassembly is connected to parameterizable input signal filtering for digital input signals, the function of the parameterizable input signal filtering being integrated in the application program of the second microcontroller. 
     The first and second microcontrollers communicate via a serial communication interface. 
     For fast signal transmission between the first and second microcontrollers, for example if the speed of serial transmission via the communication interface does not suffice, the first microcontroller is connected to the second microcontroller via parallel digital signal lines in another advantageous refinement of the central subassembly according to the invention. 
     The three electronic subassemblies in the central subassembly are each preferably arranged on a separate carrier which is in the form of a printed circuit board. The third carrier with the third electronic subassembly is preferably arranged between the second carrier with the second electronic subassembly and the first carrier with the first electronic subassembly. 
     The first and second carriers of the central subassembly are mechanically and electrically connected to the third carrier. The carriers are preferably soldered to one another for the purpose of mechanical and electrical connection; the carriers are connected by means of soldered pins, for example. This dispenses with the plug connection between the individual carriers and better mechanical stability is achieved. 
     The carriers are arranged essentially at right angles to one another, the third carrier which accommodates the voltage supply and the interface for connecting the external input and output modules being arranged between the second carrier, which accommodates the internal input and output modules, and the first carrier which accommodates the central processing unit. 
     In one preferred embodiment of the central subassembly, only the first and third carriers have connecting elements, preferably terminals, plug connectors or terminal blocks which can be plugged or soldered, for example for connecting external signals from further external expansion modules which are in the form of input and output modules, for example. The number of plug connections between the three electronic subassemblies or carriers is thus reduced since the carriers are soldered to one another and the electrical connection between the carriers is ensured without additional plug connections. 
     In one preferred embodiment of the central subassembly, the Ethernet interface and/or an apparatus in the form of a slot for accommodating accessories which can be retrofitted is/are also provided on the first carrier. The accessories which can be retrofitted may be interchangeable printed circuit boards for further interface circuits or memory cards or for accommodating a real-time clock. 
     The simplified mechanical structure of the central subassembly with respect to the integration of the functionally different subassemblies on three carriers according to their functions makes the production of the central subassembly cost-effective since the electronic subassemblies arranged on the different carriers can be produced using the respective optimally suitable soldering process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention as well as advantageous refinements, improvements and further advantages of the invention shall be described and explained in more detail using the embodiments illustrated in the following figures, in which: 
         FIG. 1  shows an exemplary automation device, 
         FIG. 2  shows an exemplary design of the hardware structure of the central subassembly, 
         FIG. 3  shows, by way of example, the design of the first electronic subassembly, 
         FIG. 4  shows, by way of example, the design of the second electronic subassembly with the inputs and outputs, 
         FIG. 5  shows an exemplary design of the third electronic subassembly with the voltage supply for the central subassembly, 
         FIG. 6  shows an exemplary design of a central subassembly for a flexible expandable automation device, 
         FIG. 7  shows an exemplary design of the printed circuit boards of the central subassembly with the electronic subassemblies arranged thereon, 
         FIG. 8  shows an exemplary solution for connecting the printed circuit boards to one another, and 
         FIG. 9  shows an embodiment of the apparatus which is on the first printed circuit board and is in the form of a slot for accommodating accessories which can be retrofitted. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exemplary automation device with the central subassembly  1  according to the invention which can be expanded with a plurality of external expansion modules  2  which can be connected via an input/output bus  3  and a bus logic module  10  (illustrated in  FIG. 3 ) and are preferably in the form of external input/output modules. 
     The external input/output modules  2  each have a subassembly PCB 4 , which comprises one or more printed circuit boards and is intended to accommodate the electronic subassemblies EA 1 , EA 2  of the external input/output modules  2 , and are each connected, via an interface  4 , to the process connected to the automation device. 
     The housing  200  of the central subassembly  1  comprises three printed circuit boards PCB 1 , PCB 2 , PCB 3 . The first printed circuit board PCB 1  is intended to accommodate a first electronic subassembly  11  for a central processing unit which is formed from a microcontroller, a memory and logic modules. The logic unit for the input/output bus  3  is also arranged on the printed circuit board PCB 1 . 
     A second electronic subassembly  21  having an interface  5  for connecting the inputs and outputs of the central subassembly  1  to the process is located on the second printed circuit board PCB 2 . 
     The third printed circuit board PCB 3  is intended to accommodate a third electronic subassembly  31  having the voltage supply  6  for the central subassembly  1 . 
       FIG. 2  shows an exemplary design of the hardware structure of the central subassembly  1  having the three electronic subassemblies  11 ,  21 ,  31  arranged on the printed circuit boards PCB 1 , PCB 2 , PCB 3 . The printed circuit boards PCB 1 , PCB 2 , PCB 3  and electronic subassemblies  11 ,  21 ,  31  are mechanically and electrically connected to one another, with  FIG. 8  showing, by way of example, the connection  7  between the printed circuit boards PCB 1 , PCB 2 , PCB 3 . 
     The first electronic subassembly  11  in the central subassembly  1  has connections in the form of interfaces for a serial interface  12  in the form of an RS485 interface and an Ethernet interface  13 . 
     An interface  14  for further interface circuits, for example for additional memory cards which are in the form of SD (Secure Digital) memory cards, for example, and a further interface (COM 2  RTC)  15  for connection to an additional printed circuit board for accommodating a real-time clock and/or to a second serial interface may also be optionally provided. 
     The second printed circuit board PCB 2  having the connections  5  for digital input and output signals of the connected process is electrically connected to the electronic subassemblies  11 ,  31  on the first and third printed circuit boards PCB 1 , PCB 3  via the connection  7 . 
     The voltage supply  6  is supplied to the central subassembly  1  via the third printed circuit board PCB 3 . 
     The connections for the external input/output modules via the input/output bus  3  are arranged on the third printed circuit board. 
       FIG. 3  shows, by way of example, the design of the first electronic subassembly  11  in the central subassembly  1  on the printed circuit board PCB 1 . 
     The first electronic subassembly  11  has a first microcontroller  16 , a volatile memory  17  for storing data, such as the operating system, the application program and the application program variable during the run time, a flash memory  18  for buffering the data stored in the volatile memory  17 , and an apparatus  9  for the initial configuration of the first microcontroller  16 . At least one application program PROGR and an operating system FW are respectively stored in the memories  17 ,  18 . 
     The first microcontroller  16  is provided with connections SPI, SCC 3 , SCC 4 , SMC 1 , FEC 2  for the parameterizable serial interfaces  3 ,  10 ,  12 ,  13 ,  15 , a connection IRQ 1  for voltage failure detection  19 , a voltage supply  36  which is supplied to a voltage supply  36  provided by the third electronic subassembly  31 , and a RUN/STOP switch RS which may also be in the form of a pushbutton. 
     The RUN/STOP switch RS is used to start or stop the programs in the central subassembly  1  by using the RUN/STOP switch RS to change over between RUN and STOP. 
     An RS485 interface is connected to the connection SCC 3 . The connection FEC 2  is intended for an Ethernet interface  13  and the connection SCC 4  is intended for serial communication a between the first microcontroller  16  and a second microcontroller  26 , for example of the type ATMega16, which is on the second printed circuit board PCB 2 . 
     In one particularly advantageous refinement, parallel digital signal lines b are provided for fast signal transmission between the MPC852 controller  16  arranged in the first electronic subassembly  11  and the second microcontroller  26  arranged on the second printed circuit board PCB 2 , which signal lines transmit the output signals from the MPC852 controller  16  to the second microcontroller  26  in the second electronic subassembly  21  via the address/data control bus  8  and the data or signal memory  40 . 
     Further parallel digital signal lines c which advantageously make it possible to quickly transmit the digital process signals guided via the second printed circuit board PCB 2  can also be connected to a further connection IRQ 2  of the MPC852 controller  16 . 
     The connections SMC 1  and Port 1  of the first microcontroller  16  are optionally connected to an additional printed circuit board for accommodating a real-time clock RTC and/or to a second serial interface COM 2  via a plug connection which is arranged on the third printed circuit board PCB 3  and is intended for a further interface  15 . 
     According to  FIG. 3 , an MPC852 controller from the PPC family is shown by way of example as the first microcontroller  16 . PPC (PowerPC) is representative of the microcontroller technology used. The connections SPI, SCC 3 , SCC 4 , SMC 1 , FEC 2  for the serial interfaces  3 ,  12 ,  13 ,  15  of the MPC852 controller mentioned as an example can also be used in another assignment or other microcontroller types from the PPC family or microcontroller types from other microcontroller families can also be used. 
     According to the invention, the data of the central subassembly  1  of the automation device are stored in a non-volatile manner by virtue of the remanent data being stored in the volatile memory  17  in the operating state of the central subassembly  1  and being used by an application program PROGR of the MPC852 controller  16 , which program is stored in the memory. The application program PROGR is executed by the MPC852 controller  16 . 
     According to the invention, a first function which stores the remanent data in the flash memory  18  when the voltage supply  6  for the central subassembly  1  fails is integrated in the application program PROGR. 
     A second function which copies the data which have been previously stored in the flash memory  18  to the volatile memory  17  again when the voltage returns using the second function is also integrated in the application program PROGR. 
     The interchange of data between the flash memory  18  and the MPC852 controller  16  and the interchange of data between the volatile memory  17 , the flash memory  18  and the apparatus  9  for initializing the initial configuration of the first microcontroller  16  are carried out via an internal address/data control bus  8 . 
     The address/data control bus  8  is also connected to indication means  50 , for example for indicating fault messages and/or the operating state of the central subassembly  1 , via a data or signal memory  40 . 
     Like the MPC852 controller  16  (at the connection SPI) too, the data or signal memory  40  is connected to a bus logic module  10  for adapting the control signals from the input/output bus  3 . 
     The bus logic module  10  is in the form of a hard-wired logic unit and is intended to connect further external input/output modules via the input/output bus  3 . 
     The MPC852 controller  16  may optionally have a connection for further interface circuits  14 , for example for additional memory cards. 
       FIG. 4  shows, by way of example, the design of the second electronic subassembly  21  with the inputs and outputs DI, DO, AI, AO for the connected process, which electronic subassembly is arranged on the second printed circuit board PCB 2 . 
     The levels of the signals are converted at the internal inputs/outputs or input and output circuits  601 ,  602 . Typical levels on the process side are 0 or 24 V DC for digital signals or 0 to 10 V or 0 to 20 mA for analogue signals. The digital inputs DI and digital outputs DO are insulated from the potential of the second microcontroller  26  with DC isolation  27 . 
     The second electronic subassembly  21  with the second microcontroller  26  arranged therein is connected to the first microcontroller  16  by means of the connection a via the serial interface. 
     The second microcontroller  26  may also be connected to the first electronic subassembly  11  via the signal lines b, c. 
     Parallel digital signal lines b are provided for fast signal transmission between the first microcontroller  16  arranged in the first electronic subassembly  11  and the second microcontroller  26  arranged on the second printed circuit board PCB 2 , which signal lines transmit the output signals from the first microcontroller  16  to the second microcontroller  26  in the second electronic subassembly  26  via the data or signal memory  40  arranged in the first electronic subassembly  11  and the address/data control bus  8 . 
     The further parallel digital signal lines c are provided for the purpose of making it possible to rapidly transmit the digital process signals guided via the second printed circuit board PCB 2  to the first microcontroller  16 . 
     In one particular refinement, the second microcontroller  26  is connected to parameterizable input signal filtering for filtering the digital input signals. The input signal filtering is implemented as one of the functions of the operating software FW 2  for the second microcontroller  26 . 
     The analogue input signals AI provided by the process and the analogue value outputs AO provided by the central subassembly  1  can optionally be guided via the second microcontroller  26 . In this case, the analogue input signals AI and the analogue value outputs AO partially use the hardware structure of the second microcontroller  26 . The analogue input signals AI are detected using an analogue/digital converter ADC of the second microcontroller  26  and are processed by the operating software FW 2 ; output values for the analogue output are processed by the operating software FW 2  and are transmitted to an additional digital/analogue converter DAC via the inputs/outputs Port 4  of the second microcontroller  26 . This considerably reduces the used amount of computation power of the first microcontroller  16 . 
       FIG. 5  shows an exemplary design of the third electronic subassembly  31  with the voltage supply for the central subassembly  1 . 
     The voltage supply for the central subassembly  1  is usually supplied with a 24-V input signal which is converted into a system voltage signal or voltage supply signal  36  (typically 3.3 V) for the microcontrollers  16 ,  26  using a first voltage converter  32 . 
     The first voltage converter  32  also provides a 24-V output signal and the voltage failure signal  34  for the first microcontroller  16 . 
     The voltage supply for the central subassembly  1  may optionally also have a power supply unit or a second voltage converter  33  which converts an AC voltage signal, for example 110-240 V AC, into a DC voltage signal, for example 24V DC, and provides the automation device with the 24-V DC voltage signal for the first voltage converter  32  in the form of a 24-V output signal. 
       FIG. 6  shows an exemplary design of the housing  200  of the central subassembly  1  for a flexible expandable automation device for controlling and/or monitoring a technical process, the third electronic subassembly  31  for supplying voltage to the central subassembly  1  being arranged on the lower part  300  of said housing, and a housing front side  400 . 
     The serial interface  12 , the Ethernet interface  13 , an apparatus  500  which can preferably be covered and is in the form of a slot for accommodating the accessories which can be retrofitted, a plug  510  for this apparatus and connecting elements  20  are arranged on the housing front side  400 . 
     In order to accommodate interchangeable printed circuit boards for further interface circuits, for example for an additional serial interface, the apparatus  500  which can be covered and has the slots is provided in the form of a socket for memory cards and/or for accommodating a printed circuit board for a real-time clock. 
     Furthermore, the housing front side  400  has indication elements  50  for indicating the input and output modules, which elements are in the form of optical waveguides. The optical waveguides are provided for the purpose of focusing the light at a defined point and contactlessly transmitting it to the front side  400  of the central subassembly  1 . The light which is focused in the optical waveguides used thus advantageously results in the light being output only at one point on the front side  4  of the central subassembly  1 . 
     In one particular embodiment of the central subassembly  1 , the latter is intended for wall mounting. For this purpose, the third printed circuit board PCB 3  and the housing lower part  300  are provided with at least one aperture  66  which is intended to accommodate fastening means, preferably screws, for wall mounting. 
       FIG. 7  shows an exemplary design of the printed circuit boards PCB 1 , PCB 2 , PCB 3  of the central subassembly  1  with electronic subassemblies  11 ,  21 ,  31  for a central processing unit, a voltage supply  60  and internal input and output modules, which subassemblies are arranged on said printed circuit boards. 
     The three electronic subassemblies  11 ,  21 ,  31  in the central subassembly  1  are each arranged on a separate printed circuit board PCB 1 , PCB 2 , PCB 3 . The third printed circuit board PCB 3  having the voltage supply for the central subassembly  1 , which is opposite the housing front side  400  of the central subassembly  1 , is arranged, according to the invention, on the housing lower part  300  between the first printed circuit board PCB 1  and the second printed circuit board PCB 2 . 
     The printed circuit boards PCB 1 , PCB 2 , PCB 3  are arranged essentially at a right angle to one another, the third printed circuit board being arranged between the first printed circuit board PCB 1 , which accommodates the central processing unit and the Ethernet interface, and the second printed circuit board PCB 2  which accommodates the internal input and output modules with the connecting element  20 . 
     The indication means  50  comprising a first optical waveguide  51  and a second optical waveguide  52  are respectively formed on the first and second printed circuit boards PCB 1 , PCB 2  of the central subassembly  1 . 
     Accessories  500  and  510  which can be retrofitted can be connected to the electronic subassembly  11  via plugs on the first and third printed circuit boards PCB 1 , PCB 3 . 
       FIG. 8  shows the electrical and mechanical connection  7  of the printed circuit boards PCB 1 , PCB 2 , PCB 3  of the central subassembly  1  which are at a right angle to one another as well as the arrangement of the optical waveguides  51 ,  52  on the first and second printed circuit boards PCB 1 , PCB 2  and the plug  12  for a communication interface and the plug  3  for the input/output bus. 
     In order to connect the printed circuit boards PCB 1 , PCB 2 , PCB 3  to one another, the first and second printed circuit boards PCB 1 , PCB 2  have, in one preferred embodiment, a multiplicity of curved pins which are guided through openings provided in the third printed circuit board PCB 3  and are soldered using a wave soldering process, for example. 
     The printed circuit boards PCB 1 , PCB 2 , PCB 3  are preferably electrically connected using solder pins. 
     The above-described electrical and mechanical connection  7  of the printed circuit boards PCB 1 , PCB 2 , PCB 3  arranged in the central subassembly  1  dispenses with expensive plug connections and better mechanical stability is achieved. 
     The aperture  66  for accommodating fastening means for mounting the central subassembly  1  on a wall is also shown, by way of example, on the third printed circuit board PCB 3 . 
       FIG. 9  shows an embodiment of the apparatus  500 , which can be covered and is on the first or third printed circuit board PCB 1 , PCB 3 , in the form of a slot for accommodating at least one printed circuit board  544  which can be retrofitted, the printed circuit board  544  being intended, for example, for additional interfaces or memory cards and/or to accommodate a real-time clock. 
     In a first embodiment  542  of the apparatus  500 , the printed circuit board  544  which can be retrofitted can be inserted, for example, into a socket formed from a U-shaped rail  545 . 
     In another embodiment  543 , the apparatus  500  for accommodating the printed circuit board  544  which can be retrofitted is formed from two elongate rail-shaped elements  546  between which the printed circuit board  544  which can be retrofitted is inserted. 
     In order to accommodate the printed circuit board  544 , the elongate cuboidal elements  546  or the U-shaped rail  545  is/are bevelled or rounded at its/their inner ends facing the printed circuit board  544  to be inserted in order to thus facilitate the accommodation of the printed circuit board  544 . 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Central subassembly 
           2  External expansion module, external input/output module 
           3  Input/output bus, plug for input/output bus 
           4  Interface between the expansion modules and the process 
           5  Interface between the central subassembly and the process 
           6  Voltage supply for the central subassembly 
           7  Connection between the carriers 
           8  Address/data control bus 
           9  Apparatus for initializing the initial configuration 
           10  Bus logic module 
           11  First electronic subassembly 
           12  Serial interface 
           13  Ethernet interface 
           14  Interface for accessories which can be retrofitted 
           15  Further interface 
           16  First microcontroller 
           17  Volatile memory 
           18  Flash memory 
           19  Connection for voltage failure detection signal 
           20  Connecting elements 
           21  Second electronic subassembly 
           26  Second microcontroller 
           27  DC isolation 
           31  Third electronic subassembly 
           32  First voltage converter 
           33  Second voltage converter 
           34  Voltage failure signal 
           36  Voltage supply for the microcontroller 
           40  Data or signal memory 
           50  Indication element 
           51  First optical waveguide 
           52  Second optical waveguide 
           60  Voltage supply for the central subassembly 
           66  Aperture 
           200  Housing 
           300  Housing lower part 
           400  Housing front side 
           500  Apparatus for accommodating accessories which can be retrofitted 
           510  Plug for apparatus for accommodating accessories which can be retrofitted 
           541  Opening for accommodating additional printed circuit boards 
           542  First embodiment for accommodating an additional printed circuit board 
           543  Second embodiment for accommodating an additional printed circuit board 
           544  Additional printed circuit board 
           545  Socket, U-shaped rail 
           546  Elongate cuboidal element 
           601 ,  602  Input and output circuits 
         a Connection via serial interface for communication between the first microcontroller and the further microcontroller 
         b Parallel digital signal lines for fast output signals from the first electronic subassembly 
         c Parallel digital signal lines for fast direct input signals for the first electronic subassembly 
         ADC Analogue/digital converter 
         DAC Digital/analogue converter 
         FW Operating system/firmware 
         FW 2  Operating software/firmware 
         PROGR Application program 
         PCB 1  First carrier for accommodating the first electronic subassembly in the central subassembly 
         PCB 2  Second carrier for accommodating the second electronic subassembly in the central subassembly 
         PCB 3  Third carrier for accommodating the third electronic subassembly in the central subassembly 
         PCB 4  Carrier for accommodating the electronic subassembly for the external input/output modules 
         PROGR Application program 
         RS Run/stop switch 
         SLS SLS signal 
         EA 1 , EA 2  Electronic subassemblies of the external input/output modules 
         SPI, SCC 3 , SCC 4 , Connections for parameterizable serial interfaces of the 
         SMC 1 , FEC 2  microcontroller