Abstract:
The digital interface unit ( 1 ) for control of a peripheral device, especially for controlling a magnetic valve for an injection device, includes a plurality of output registers ( 2  to  5 ), which store and output a set of control variables applied to the input sides of the respective output registers in response to a control signal ( 18 , MST E). So that the control variables are output from the output registers exactly simultaneously even though they are received sequentially, at least one group of buffer registers ( 12  to  15, 24  to  27 ) is connected to the output registers ( 2  to  5 ). The buffer register or registers provides intermediate storage for the control variables prior to output from the interface unit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a digital interface unit for control of a peripheral device and, more particularly, to a digital interface unit for control of a peripheral device, especially a positioning device, comprising a data input for receipt of a control value or values for the peripheral device, an output register or registers for storing the control value or values received via the data input and for preparation of the control value or values for output to the peripheral device, wherein the output register or registers has a first control input and means for outputting the control value or values in response to a signal at the first control input. 
     2. Prior Art 
     In microprocessor systems digital interface units are used for control of peripheral devices, which adapt the internal data bus of the microprocessor system to the external data bus between the microprocessor system and the peripheral device. An output circuit for a microprocessor system, for example, is known from Philippow, “Taschenbuch der Elektrotechnik” (Pocketbook of Electrical Engineering), 3rd Ed., Vol. 3, p. 1126. This output circuit has an output register, which receives a data word to be output via the internal data bus of the microprocessor system, prepares it and places it on the external data bus for the peripheral device. The control of the data output occurs by means of a control signal designated a data strobe signal, which controls the output register for importing the data word on the internal data bus, so that all data bits of the new data word appear at exactly the same time on the external data bus, which is important especially for controlling a positioning device, since otherwise the positioning device receives an incorrect control value for a short time. 
     It is however disadvantageous that the interface unit blocks the internal data bus of the microprocessor system during output of a new data word, since the new data word must be present on the internal data bus at exactly this time. Hardly any time exists for this. It is also not possible, for example, to already transfer the new data word to the interface unit prior to the provided time point and to employ the internal data bus subsequently for other purposes. Accordingly the usefulness of the internal data bus of the microprocessor system is limited. 
     In an interface unit with several output registers it is thus not possible to transmit a complete set of several new control values simultaneously to all output registers, since the individual output registers must be loaded sequentially over the internal data bus and the respective new control values immediately imported. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an interface unit for controlling a peripheral device which limits the usefulness of the internal data bus of the microprocessor system as little as possible and despite the output of a new data word guarantees that all data bits are output simultaneously so that incorrect control of the peripheral device is prevented. Especially the simultaneous output of a complete set of new control values should be possible with an interface unit according to the invention provided with several output registers. 
     This object, and others which will be made more apparent hereinafter, are attained in a digital interface unit for control of a peripheral device, especially a positioning device, comprising a data input for receipt of a control value for the peripheral device, an output register for storing the control value received at the data input and for preparation of the control value for output to the peripheral device, wherein the output register has a first control input and means for outputting the control value input to it on activation of or in response to a signal at the first control input. 
     According to the invention a buffer register is connected between the data input and the output register for intermediate storage of the control value applied to the control input of the output register. 
     The buffer register provides the advantage that a new data word can be received from the internal bus independently of the output of a data word from the unit, i.e. at any time. 
     The term “peripheral device” here means any electrically controllable component, device or adjusting member. The interface unit according to the invention is preferably used for control of magnetic valves in injection units. 
     In a preferred embodiment of the invention the interface unit has several parallel output registers, which control respective peripheral devices or contain respective control values for the same peripheral devices. During the control of the magnetic valve the individual output registers, for example can receive the electric current passing through the magnetic valve and control parameters for regulation of the magnetic valve. Each output register is connected to a respective buffer register. The input side of the buffer registers are connected with the address bus of the microprocessor system to allow selective addressing. 
     In another advantageous aspect of the invention transmission of individual data words from the microprocessor system to the interface unit does not occur individually at the predetermined time point, but a sequence of several data words is transmitted one after the other to the interface unit and intermediately stored there in a data memory. The internal data bus of the microprocessor system is rarely blocked, which is especially notable for control magnetic valves, since the sequence of control values is not varied during the closing process of the magnetic valve, so that the control values of a closing sequence can be transmitted without loss of function to the interface unit. After transmission of a sequence of control values to the interface unit, the individual controls values are then sequentially read out from the data memory and written into the output register. 
     The control of the sequential output of the intermediately stored control values to the output register occurs preferably via a control signal which is generated by the microprocessor system. The microprocessor system in this case of course has no further influence on the sequence and the control values of the intermediately stored sequence itself during the individual output, however the microprocessor system can still control the time of output. The control signal can be fed to the interface unit by a binary control line, whereby data and address buses of the microprocessor system advantageously remain free. 
     According to another aspect of the invention the interface unit has two operating modes. One of the operating modes allows a direct write of a new data word into the input side of the buffer memory, while a complete sequence of data words is transferred in another operating mode. In that mode a multiplexer is connected to a respective output register, which either directly connects the output register with a buffer memory or allows the storage of a complete sequence with intermediate switching of the data memory. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiments, with reference to the accompanying figures in which: 
     FIG. 1 is a block diagram of an interface unit according to the invention for control of a magnetic valve, 
     FIG. 2 is a block diagram of a microprocessor system for controlling the interface unit of FIG. 1; and 
     FIG. 3 is a graphical illustration of several control signals of the interface unit of FIG.  1  and of the electrical current through the magnetic valve in several stages of a closing opening process. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The digital interface unit  1  shown in FIG. 1 controls a magnetic valve and has four output registers  2 ,  3 ,  4  and  5  that determine the behavior of the magnetic valve. The data register  2  contains the actual control value for the current strength of the current through the magnetic valve. Control values are contained in the control register  4  and the pre-control register  5 , which are required for the magnetic valve, especially for a P-controller. The BIP register  3  contains a control value, which is necessary for correct closing of the magnetic valve, especially for detection of a closed state of the magnetic valve. 
     For clarification of the operation of the interface device  1  a closing process of the magnetic valve is described in the following with the aid of FIG.  3 . The behavior of the electrical current i during the individual stages of the closing process is shown in FIG.  3  and described hereinbelow. 
     The closing process of the magnetic valve begins at the time point t 0  with a so-called preliminary application of current to the magnetic valve which lasts until time point t 1 . During this preliminary application of current the electrical current i is increased in a controlled manner by a P controller, so that a control value must be contained in the data register  2 , the pre-control register  5  and the control register  4  of the interface unit  1  during the preliminary application stage. 
     After that the magnetic valve is closed in the primary closing stage with a steep current increase, which lasts until the time point t 2 . Herein no regulation occurs. 
     Finally the electrical current i is reduced to a smaller value which remains constant from t 2  to t 3 . In this state the shifting of the magnetic valve into its final configuration is detected. The pre-control register  5 , the control register  4  and the BIP register  3  are relevant. 
     The electrical current i through the magnetic valve is reduced further to a still lower value in the next stage from t 3  to t 4 , in order to save current, but of course the magnetic valve remains closed. The control register  4  and the pre-control register  5  are irrelevant in this stage. 
     The data register  2  of the interface unit  1  then contains the null control value at time point t 4 , so that the electrical current i through the magnetic valve drops to zero and the magnetic valve is opened again. The control register  4  and the pre-control register  5  are irrelevant for this. 
     From the previous description it is apparent that the contents of one or more output registers  2  to  5  must be changed during transition between the individual stages. During a change in the contents of the several registers it is important that the individual output registers  2  to  5  receive the new control values at exactly the same time, since a time-delayed change of an individual register contents could lead to an undesirable behavior of the magnetic valve. The change in the register contents thus does not occur by sequential writing of the new values to the individual output registers  2  to  5 , but by an exactly simultaneous transmission of the new control values from a pre-switched memory structure, that functions as a buffer and can be loaded with the new control values prior to that sequentially. The transmission of the new control values into the output registers  2  to  5  is triggered by a microprocesor system  6  shown in FIG. 2, so that a control line (MST E, Magnetic valve Strobe Input) is connected with the registers. 
     The interface unit  1  shown in FIG. 1 has two different modes of operation, which either provide direct loading of the output registers  2  to  5  by the microprocessor system  6  or allow a buffering of several sets of control values. one after the other in the interface unit  1 , which can define a complex current curve. The mode of operation of the interface unit  1  can be selected by means of a control line  7  (FM DIS). 
     The first operation mode subsequently described here provides a direct loading of the output registers  2  to  5  and is used essentially for test purposes, since the effect of the changed control values on the magnetic valve can be immediately observed. 
     In this mode of operation the input side of the output registers  2  to  5  is connected by means of respective multiplexers  8 ,  9 ,  10  and  11  with respective buffer registers(pre-set register)  12 ,  13 ,  14  and  15 , which provide intermediate storage of the new control values prior to writing in the output registers  2  to  5 . The outputs of the buffer registers  12  to  15  are switched to the multiplexers  8 ,  9 ,  10  and  11  by input of the control line  7 . 
     The writing of the new control values into the buffer regions  12  to  15  occurs by means of the microprocessor system  6 , which is connected with the interface unit  1  by means of a data bus  16 , an address bus  17  and several control lines  18  to  21 . First the microprocessor system  6  addresses the desired buffer register  12 ,  13 ,  14  or  15  by means of the address bus  17  and simultaneously puts the desired control value on the data bus  16 . Moreover the control lines  20  (CS E, Chip Select Enable) and  21  (RW E, Read/Write Enable) are activated in order to control the interface unit  1  for preparation of the transmitted control values. The interface unit  1  decodes the address value on the address bus  17  using an address decoder  22  and controls one of the buffer registers  12  to  15  accordingly, in so far as the interface unit  1  is not found in another operating mode and accordingly addresses other registers. The buffer register  12 ,  13 ,  14  or  15  addressed in this manner receives the new control value from the data bus  16  and stores it. The new control values are written sequentially in this manner into the buffer registers  12  to  15 . The individual buffer registers  12  to  15  can be separately accessed, which has the advantage that when only one control value is changed only one of the buffer registers  12 ,  13 ,  14  or  15  is newly written. Only one write/read process is required. The individual receipt of the new control values intermediately stored in the buffer registers  12  to  15  occurs simultaneously by all output registers  2  to  5 , since the microprocessor system  6  activates the control line  18 (MST E, Magnetic valve Strobe Input). The output registers  2  to  5  receive new control values from the buffer registers  12  to  15  at their inputs as is illustrated in FIG.  3 . 
     In the following now the second mode of operation is described, in which several sets of control values one after the other are stored in the interface unit  1 , which define a complex current curve, whereby transmission of control values from the microprocessor system  6  to the interface unit  1  is required only for initializing or activating the operating cycle of the magnetic valve, but not for each state change of the magnetic valve. The address bus  17  and the data bus  16  of the microprocessor system  6  thus remains free during normal operation and can be used for other purposes. 
     The activation of an operating cycle occurs by means of the microprocessor  6 , since it addresses an address register  23  (“File Address Data Register”) and transmits an address value by means of the data bus  16 , which is subsequently used for addressing one of the four additional buffer registers  24  to  27  (“File Register”). Subsequently the microprocessor system  6  addresses a data register  28  (“File Data Register”) and puts the new control value on the data bus  16 . The new control value is written into the data register  28 . Subsequently when the address value is stored in the address register  23  and the associated control value is written into the data memory  29 , the several sets of control values can be received and thus define a complete operating cycle of the magnetic valve. 
     The retrieval of the operating cycle stored in the data memory  29  in the form of control values is controlled by the microprocessor system  6 , when the control line  19  (FST E, File Strobe Enable) activates it. A decoder  30  decodes an address value stored in the data memory  29  during each activation of the control line  19  (FST E) and activates the associated buffer register  24 ,  25 ,  26  or  27 , which takes the associated control values from the data memory  29 . In this way a complete set of control values is read out from the data memory  29  and into the registers  24  to  27 . Prior to the retrieval of the new control values from the data memory  29  a 5-bit counter  31  is reset (e.g. by setting of a bit in one of the registers (FM DIS)). Subsequently the counter  31  is incremented on each activation of the control line  19  (FST E). The control line  7  (FM DIS) controls the multiplexers  8  to  11  to connect the buffer registers  24  to  27  with the output registers  2  to  5 . The receipt of the new control values in the output registers  2  to  5  occurs as in the first operating mode, since the microprocessor system  6  activates the control line  18  (MST E) connected with the output registers  2  to  5 . The output registers  2  to- 5  receive the new control values exactly at the same time from the connected buffer registers  24  to  27 . Preferably in this operating mode the fact is that several sets of control values can be stored in the data memory  29 , for example which control the operating cycle of the magnetic valve shown in FIG.  3 . During normal operation no transfer of new control values from the microprocessor  6  to the interface unit  1  is required. 
     FIG. 2 shows an advantageous embodiment of the microprocessor system  6  for control of the interface unit  1 . The microprocessor system  6  has a commercial microprocessor  32  acting as core component, which is shown here only schematically and communicates with the interface unit  1  via the address bus  17  and the data bus  16 . The microprocessor  32  has the purpose in the scope of the present invention to transmit the control values of a complete operating cycle of the magnetic valve into the data memory  29  of the interface unit  1 . Subsequently the microcomputer  32  has no further control over the activation of the opening and closing of the magnetic valve. 
     The microprocessor system  6  furthermore has a so-called microprocessor engine  33  embodied as a simple computer, which operates the control line  18  and the control line  19  and thus controls reading of the intermediately stored control values from the data memory  29  to the buffer registers  24  to  27  and also the receipt of the control values in the output registers  2  to  5  from the buffer registers  24  to  27  or  12  to  15 . The microcomputer  32  however has the ability to transfer commands to the micro engine  33  via the data bus  16 , so that it control subsequently the interface unit  1 . 
     The disclosure in German Patent Application 198 30 625.3 of Jul. 9, 1998 is incorporated here by reference. This German Patent Application describes the invention described hereinabove and claimed in the claims appended hereinbelow and provides the basis for a claim of priority for the instant invention under 35 U.S.C. 119. 
     While the invention has been illustrated and described as embodied in an improved digital interface unit, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.