Abstract:
The mailing machine includes a microcontroller system for executing machine control algorithms during each control cycle and user interface algorithms. Each control cycle is divided into first discrete time intervals sufficient to allow completion of the respective control algorithms, and a second time interval for execution of user interface algorithm and, if required, completion of the user interface algorithm during subsequent control cycles.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to real time machine control systems and, more particularly, to such control systems particularly suited for the control of a postage meter mailing machine. 
     A known mail processing control system is illustrated in U.S. Pat. No. 4,959,600, entitled “Microprocessor System Controller For Mail Processing System Applications” and U.S. Pat. No. 5,331,538, entitled “Mail Processing System Controller”. The control system is principally partitioned into two independent systems. The first system is the host microcontroller system for controlling the man machine interface and external communication functions and a motor control system for controlling and coordinating the operation of a number of motors pursuant to sensor input. In order to accommodate the data process control needs of the system motors in real time, the motor control system is divided into control cycles. Each control cycle is set to run at a fixed period. Each period is further divided into a number of intervals which are assigned to perform data process functions for a particular subsystem. For example, each control cycle is set to be initiated every 2 millisecond. During each control cycle, nozzle command generation is allocated 45 microseconds, position servo control is allocated 40 microsecond, sensor input is allocated 30 microseconds, and so forth. At the end of each cycle a 500 microsecond timer interrupt routine is executed during which a system check is performed to assure that the system software is properly executing. The host microcontroller system performs in a conventional manner to control non-real time functions such as keyboard and display communication and external communication. A shared random access memory is used to allow access to necessary information between the two microcontroller systems. The described known mailing machine control system requires a number of microprocessors of sufficient speed to perform all the necessary data processing. Consequently the mailing machine control system represents a substantial cost. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to present a mailing machine control system which provides both motor control and external system control utilizing a single microcontroller system. 
     It is a further objective of the present invention to present a mailing machine control system which can perform real time machine control and man machine interface (MMI) control functions within a single control cycle of the microcontroller system. 
     It is a still further objective of the present invention to present a system control architecture representing a low-cost solution for control of a mailing machine which is flexible enough to be reused for a variety of mailing machine options providing the benefit of software and hardware reusability. 
     It is a still further objective of the present invention to present a low-cost software control system and software architecture that enables a high performance real-time machine control system that has a discrete time-slice architecture, with fully featured user interface software to drive a low-cost machine application. 
     A postage meter system in accordance with the present invention includes a mailing machine, which serves as a platform for the meter unit and printing unit. The mailing machine includes a microcontroller system which is responsible for controlling a number of system operations. Preferably, the mailing machine includes a feeder section for receiving a stack of envelopes and presenting a plurality of the envelopes to a singulation station. The singulation station is responsible for withdrawing a single envelope in a seriatim manner from the envelopes presented. An envelope is then transported to an integrated scale where the envelope may be weighed. The envelope is then presented to the printing station. The printing unit then prints a postage indicia and any other additional information, such as, an ad slogan, delivery address or bar code, on the envelope. In a preferred configuration, it is contemplated that printing will occur during relative motion between the envelope and a digital printing unit, such as an ink jet printer. Therefore, the microcontroller system of the mailing machine will be responsible for relatively precise control of the motors responsible for transporting the envelope. It should be appreciated that it is an objective of the mailing machine control system to promote maximum machine through-put. 
     The mailing machine also contains the man machine interface system which enables interfacing a keyboard and display, non-secure accounting system, communication to external printing devices, modem communication for data center communication and other subsystem functions. 
     Metering is provided by two independent units which are a meter vault and a printer. The vault accounts for dispensed funds used during posting of each envelope. Communication between the mailing machine, vault and printer is facilitated through a printer interface unit. The printer interface serves as a junction board for the mailing machine, meter vault, graphics interface, if present, and print head. The printer interface provides the connections for a serial communication linkage and unregulated DC power from the mailing machine to the meter vault, transfers print command and status signals between the mailing machine and print head, interfaces the graphics interface to the print head, supports a unique serial link between the meter vault and print head, and regulates logic and print nozzle power from the mailing machine to the print head. 
     The mailing machine microcontroller system is required to provide machine control as well as interface control. Within the system, machine control and user interface control are combined in a discrete time-slice architecture to achieve the desired functionality. Machine control portions of the system are driven by a discrete timer which causes the control algorithms to execute within a specified time interval. When the discrete time interval occurs, the machine control algorithms execute to completion. These algorithms complete prior to the occurrence of the next discrete time interval. During the time between the completion of the motion control algorithms and the occurrence of the next discrete time event (MMI interval), the software algorithms for controlling the user interface and other subsystem functions are allowed to execute, if required. The algorithms to be executed during MMI interval are not required to be completed during the MMI interval. Completion of the MMI algorithms can await the next MMI interval of the subsequent control cycle. If there are no MMI algorithms presented, then the microcontroller system queues the microcontroller system defaults during that MMI interval to perform a timer interrupt routine to check system operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is schematic of a mail processing system in accordance with the present invention. 
     FIG. 2 is a schematic of the microcontroller system for a mailing machine in accordance with the present invention in combination with a meter vault, printer interface and printer particularly suited to the present invention. 
     FIG. 3 is an expanded schematic of the mailing machine microcontroller system in accordance with the present invention. 
     FIG. 4 is a time diagram of the mailing machine microcontroller system in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the postage meter system, generally indicated as  11 , includes a mailing machine base  12 . The mailing machine base  12  is of any suitable known design and, in the preferred embodiment, includes a feeder  13 , singulator  14  and scale  15  positioned serially along a mail flow path. Following the scale  15  is a print station at location A which is followed by a stacker  17 . Any suitably designed feeder  13 , singulator  14 , scale  15  and stacker  17  may be used. The operation of the respective feeder  13 , singulator, printer transport and envelope transport (not shown) is under the control of a mailing machine controller  21 . Power is provided by a conventional power supply  19 . It should be appreciated that the mailing machine microcontroller  21  is responsible for providing real time motor control function to motors  81  and  83  (refer to FIG.  3 ), in addition to, non-real time control of man machine interface functions as keyboard and display, unsecured departmental accounting (not shown) and external communications. As depicted in FIG. 1, a rates memory (PROM  22 ) is detachably mounted to the mailing machine controller  21  to provide rate information to the mailing machine controller  21  in any suitable conventional manner. 
     Also, housed in the mailing machine is a printer interface  23 , graphics interface  25 , meter vault  24  and print head/controller  27 , hereafter referred to as print head  27 . The print head  27  is mounted to a pair of rails  30  and  31  by any suitable means to be positionable, by any conventional means (not shown) in response to a motor  81  or  83  between a first position “A” which is the print position, a second position “B” which is a tape print position, and a third position “C” which is a cleaning position. At position “C” the print head  27  is brought into contact with a nozzle cleaning system of any suitable design for cleaning. The positioning of the print head  27  along the rails  30  and  31  is under the control of the mailing machine controller utilizing any suitable conventional control means. 
     Also, the mailing machine base  12  includes provisions for allowing the external interface of an external interface unit (EIU  26 ) to the printer interface  23  by any conventional means. The EIU  26  provides additional microprocessor functionality to the system  11  utilizing any suitable method. 
     Referring to FIG. 2, the meter vault  24  includes a source accounting memory  40  and  41 , program memory  42 , application specific integrated circuit (ASIC)  13 , CPU controller  44 , and keyboard/display  45 . The keyboard/display  45  is proved to the meter vault  24  to facilitate manual meter recharging. 
     The communication port  46  is modified to include an extra pin for receiving DC power from the mailing machine. It should be appreciated that the keyboard and display  45  is provided an operator or postal agent a means of recharging the accounting registers of the accounting memory  40  and  41  through the keyboard in any suitable conventional manner. 
     The mailing machine controller  21 , among other things which will be described in more detail subsequently, includes a controller CPU  50 , system memory units, generally indicated as  51 , user input/output  53 , motor control ASIC  54 , sensor control ASIC  55 . Also, provided is a scale interface  56  and UART interface  57 . The UART interface  57  is of any suitable design for allowing asynchronies serial communication. Of principle concern to the preferred embodiment of the present invention is that the UART interface facilitates communication between the mailing machine controller  21  and the other system units  23 ,  24 ,  25 ,  26  and  27 . 
     The printer interface  23  serves as a junction board for the mailing machine  21 , meter vault  24 , print head  27  and a graphics interface  25 . By providing specific communication paths P 13 , P 14 , P 17 , P 37 , P 46 , P 47 , P 57  within the printer interface  23 , the individual subsystems can be isolated in such a manner to remove the necessity for interdependent security measures. Meter vault  24  communications to the print head  27  are routed through the printer interface  23  along communication path P 47 . Communications path  47  is also used to select inscriptions and slogans in conjunction with the graphics interface  25 . A printer interface path P 46  is provided for electrical communication with the EIU  26 . As aforenoted, the EIU  26  represents an external unit which can be attached to the meter vault  24  to provide enhanced capability to the meter vault  24  when the meter vault  13  is used in combination with a reduced featured mailing machine. 
     The graphics interface  25  stores graphic images representing the fixed part of the standard indicia (e.g., the eagle printed on US mail), low-value indicia, permit mail indicia, town circle (where appropriate), inscriptions, and slogans. It also stores the fonts for printing the variable data on the mail piece. 
     The print head  27  is comprised of a CPU controller  60 , nonvolatile memory units  61  and  62 , ASIC  63  and ink jet print heads  64 ,  65 ,  66 . The print head  27  prints the indicia including postage amount, digital tokens, piece count, and date as well as an optional inscription and slogan on each mail piece. The fixed part of the image, fonts for the variable parts of the image, and inscription bit-maps are programmed into the print head&#39;s NVM  61  and  62  when the print head is first installed in the mailing machine  17 . The meter vault  24  will send a message to the print head indicating the format of the town circle. The print head  27  obtains the town circle information as either a text string from the meter vault or a bit map from the graphics interface and programs its NVM with the data. For each mail piece, the meter vault  24  transfers the variable indicia information such as the postage amount, digital tokens, meter serial number, and piece count to the print head  27 . The print head controller  60  programs registers (not shown) in the ASIC  63  with this information. When the mailing machine controller  21  commands the print head to print, the ASIC  63  combines the fixed and variable parts of the image for printing by the print units  64 ,  65  and  66  utilizing any suitable technique. 
     Referring now more particularly to FIG. 3, the mailing machine controller  21  utilizes a controller  50  in bus communication with a control ASIC  70 , the motor control ASIC  54 , the sensor control ASIC  55  and memory units  71  to  73 . The control ASIC  70  includes a UART module  57  (Universal A-Synchronous Receive And Transmits) to enable serial communication and a timer module  74 . The UART module  57  is in direct communication with the scale interface  56  and, in addition, an external I/O  75  and a two channel printer interface connector  77  provided to facilitate communications with the printer interface  23  as described above. Also, provided is a connector  79  which is provided to allow connection of a rates prom  22  to the control ASIC  70 . 
     In the preferred embodiment, the mailing machine base  12  includes two motors  81  and  83  which are provided as prime movers for the various mailing machine stations. These motors  81  and  83  are in electrically responsive communication with the motor ASIC  54 . The motor ASIC  54  provides independent control of the drive output of the motors  81  and  82 . Also provided are a plurality of sensors  85  which are positioned at various points along the mail path. The sensor is directed to the sensor ASIC  55  which provided processed information to the microcontroller  50  for use by the motor control algorithms in a conventional manner. The control ASIC  70  includes a timer module  47  which provides timing signals to the controller  50 , motor control ASIC  54  and sensor ASIC  55 . 
     Referring to FIG. 4, each process control cycle is set at a discrete time of 2 ms in the preferred embodiment. Each control cycle allocates a discrete time interval for motion control (motor control, sensor sampling, subsystem control and profile generation), communications (RX/TX) through the UART Module and idle. During idle time, the microprocessor  50  can then process user interface control algorithms. The system algorithm for motor control, sensor sampling and processing, subsystem control, motor control profile generation and communication are provided sufficient time to complete. The algorithms that execute during idle time control the mailing machine user interface, message processing and perform machine synchronization and high-level control.