Control system for ophthalmic surgical instruments

What is claimed is:

1. A microsurgical control system for controlling a fluid pressure controlled microsurgical instrument, comprising:

pressure control means for coupling to a microsurgical instrument and for providing a controlled fluid pressure signal to said instrument;

digitally programmed electronic circuit means coupled to said pressure control means for defining at least two different sets of response characteristics, each set of response characteristics comprising a predefined relationship in which a plurality of different input values each bears a one to one relationship to a corresponding output value;

said electronic circuit means including means for selecting one of said different sets of response characteristics as the active set of response characteristics;

actuator means coupled with said electronic circuit means for providing an input value to said electronic circuit means in response to human actuation;

said electronic circuit means determining an output value from said input value in accordance with said active set of response characteristics and using said output value so determined to control the pressure provided to said instrument.

2. The control system of claim 1 further comprising digital memory means coupled to said electronic circuit means for storing said different sets of response characteristics, and wherein said electronic circuit includes means for selectively reading one of said sets of response characteristics from said memory means and for altering the manner in which said control system responds in accordance with the response characteristic read.

3. The control system of claim 1 further comprising a portable memory which is removably couplable to said electronic circuit means for storing at least one of said sets of response characteristics, and wherein said electronic circuit includes means for selectively reading said response characteristics from said portable memory and for altering the manner in which said control system responds in accordance with the response characteristic read.

4. The control system of claim 1 wherein said actuator means comprises a foot pedal.

5. The control system of claim 1 further including self illuminating display means for displaying surgical control information associated with said control system.

6. The control system of claim 1 wherein said actuator means comprises at least one endless digital potentiometer.

7. The control system of claim 1 further comprising a first digital memory circuit coupled to said electronic circuit means for storing at least one of said sets of response characteristics and comprising a second portable memory circuit removably couplable to said electronic circuit means for storing another of said sets of response characteristics; and

wherein said electronic circuit includes means for selectively reading said response characteristics from said first and second memory circuits and for altering the manner in which said control system responds in accordance with the response characteristic read.

8. The control system of claim 1, wherein the fluid pressure controlled microsurgical instrument is an instrument selected from the group of ophthalmic surgical instruments consisting of fragmentation emulsification instruments, cutting instruments and aspiration instruments.

9. The control system of claim 1, further comprising:

second pressure control means for coupling to a second ophthalmic microsurgical instrument and for providing a controlled fluid pressure signal to said second instrument;

third pressure control means for coupling to an ophthalmic microsurgical irrigation instrument and for providing a controlled liquid pressure flow to said irrigation instrument;

an electronic display screen on said console having at least a plurality of first distinct display regions and a plurality of second distinct display regions, with each of said first regions being capable of displaying at least a plurality of human readable characters and each of said second display regions being capable of displaying two sets of human readable characters; and

a plurality of manually actuable controller means disposed on said console at locations corresponding to predetermined regions of said display screen, said controller means including a plurality of first controllers for selecting said surgical procedures and a plurality of second controllers for selecting operating values of said microsurgical instruments.

10. A microsurgical control system for controlling at least two different ophthalmic microsurgical instruments so as to be able to perform a plurality of different surgical procedures therewith, comprising:

a console;

means on said console for connecting to at least two ophthalmic microsurgical instruments;

an electronic display screen on said console having at least a plurality of first distinct display regions and a plurality of second distinct display regions, with each of said first regions being capable of displaying at least a plurality of human readable characters and each of said second display regions being capable of displaying two sets of human readable characters;

a plurality of manually actuable controller means disposed on said console at locations corresponding to predetermined regions of said display screen, said controller means including a plurality of first controllers for selecting said surgical procedures and a plurality of second controllers, with each of said second controllers being for selecting an operating value of one of said microsurgical instruments, and with each of said second controllers having a movable control portion adapted for smooth and continuous movement through a range of positions corresponding to more than a few different operating values of one of said microsurgical instruments;

menu generating means coupled to said display screen for writing human readable characters including numbers at said second regions of said display screen indicative of operating functions and values of said microsurgical instruments and for writing predetermined human readable messages at said first regions of said display indicative of said different surgical procedures;

procedure control means coupled to said connecting means for defining and providing a plurality of predetermined and selectable ophthalmic surgical procedures for controlling said instruments, said surgical procedures corresponding to procedures indicated by said predetermined human readable messages that are written to the first regions of said display; and

procedure selection means coupled to said procedure control means and responsive to said first controllers of said controller means for causing said procedure control means to perform a selected one of said plurality of procedures.

11. The control system of claim 10 wherein said human readable messages correspond to and identify said plurality of procedures, said procedures including at least four procedures selected from the group of ophthalmic surgical procedures consisting of vitrectomy, microscissor cutting, irrigation, aspiration, illumination, fragmentation, and emulsification.

12. The control system of claim 10 wherein said menu generating means is coupled to said controller means to change said human readable messages in response to actuation of said controller means in a predetermined progression from menu to menu dependent upon which one of said controllers is depressed with respect to each menu, said progression of menus being organized so that certain menus exclude listing certain surgical procedures in individual ones of said menus when such certain procedures are normally not performed in connection with a specific surgical procedure selected from a previous menu.

13. The control system of claim 12 further comprising redefining means responsive to said plurality of first controllers and coupled to said menu generating means and to said procedure control means for causing said procedure control means to provide a different plurality of predetermined and selectable surgical procedures in accordance with a selected progression of menus which have been displayed on said display screen.

14. The control system of claim 13 wherein said redefining means includes a readily removable memory key for storing parameters used to at least in part specify the manner of operation of said two instruments during said surgical procedures.

15. A microsurgical control system for controlling any one of at least three different predetermined ophthalmic microsurgical instruments, the control system comprising:

a console having display means for displaying simultaneously a plurality of human readable messages pertaining to surgical functions for two or more ophthalmic microsurgical instruments and operating values therefor, and a plurality of manually actuable selector means arranged about predetermined regions of said display means for selecting said surgical functions and operating values, said plurality of selector means including at least a first set of switches for selecting said surgical functions, and a set of selector knobs for selecting said operating values, at least two of said knobs each having a movable control portion adapted for smooth and continuous movement through a range of positions corresponding to multiple different operating values associated with a selected one of said surgical functions; and

programmed controller means for generating said messages for display, for defining a plurality of functions and control characteristics for said selector means, and for generating signals which control the operation of each of said ophthalmic microsurgical instruments in response to the actuation of said selector means, said controller means including memory means for assigning a different operating value to at least one knob of said selector means for different ophthalmic surgical procedures.

16. The microsurgical control system of claim 15, wherein said controller means includes memory means for assigning a different function to at least one of said selector switches for different surgical procedures, and for assigning a different operating value to at least one of said selector knobs for different surgical procedures.

17. The microsurgical control system of claim 15, wherein said controller means includes circuit means for distally encoding the signals from said selector knobs, and counter means for processing said encoded signals into digital values corresponding to said operating values.

18. The microsurgical control system of claim 15, wherein said controller means includes manually removable programmable memory means for determining at least some default values of said control characteristics of said selector means, said memory means being user-programmable by actuation of selected ones of said selection means of said console.

19. The control system of claim 15, wherein said system is capable of operating at least said three instruments concurrently, and said programmed controller means includes

first pressure control means for providing a controlled fluid pressure signal to a first one of said ophthalmic instruments, and

second pressure control means for providing a controlled fluid pressure signal to a second one of said ophthalmic microsurgical instruments,

said first one and said second one of said instruments being selected from the group of ophthalmic surgical instruments consisting of cutting instruments, irrigation instruments and aspiration instruments.

Description Submit all comments and votes

MICROFICHE APPENDIX

This application includes a microfiche appendix having one microfiche and thirty-six frames.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to microsurgical and ophthalmic systems and more particularly to a programmable control system and console for operating microsurgical instruments.

Present day ophthalmic microsurgical systems provide one or more pneumatically operated (fluid pressure operated) surgical instruments connected to a control console. The control console provides the fluid pressure signals for operating the instruments and usually includes several different types of human actuable controllers for controlling the fluid pressure signals supplied to the surgical instruments. Usually included is a foot pedal controller which the surgeon can use to control a surgical instrument.

The conventional console also has push button switches and adjustable knobs for setting the desired operation characteristics of the system. The conventional control system usually serves several different functions. For example, the typical ophthalmic microsurgical system has both anterior and posterior segment capabilities and may include a variety of functions, such as irrigation/aspiration, vitrectomy, microscissor cutting, fiber optic illumination, and fragmentation/emulsification.

While conventional microsurgical systems and ophthalmic systems have helped to make microsurgery and ophthalmic surgery possible, these systems are not without drawbacks. Microsurgical and ophthalmic systems are relatively costly and are often purchased by hospitals and clinics for sharing among many surgeons with different specialties. In eye surgery, for example, some surgeons may specialize in anterior segment procedures, while other surgeons may specialize in posterior segment procedures. Due to differences in these procedures, the control system will not be set up in the same manner for both. Also, due to the delicate nature of this type of surgery, the response characteristics or "feel" of the system can be a concern to surgeons who practice in several different hospitals, using different makes and models of equipment. It would be desirable to eliminate the differences in performance characteristics between one system and the next, while at the same time providing enough flexibility in the system to accommodate a variety of different procedures. The prior art has not met these objectives.

The present invention greatly improves upon the prior art by providing a programmable and universal microsurgical control system, which can be readily programmed to perform a variety of different surgical procedures and which may be programmed to provide the response characteristics which any given surgeon may require. The control system is preprogrammed to operate in a variety of different modes to provide a variety of different procedures. These preprogrammed modes can be selected by pressing front panel buttons.

In addition to the preprogrammed modes, each surgeon can be provided with a programming key, which includes a digital memory circuit loaded with particular response characteristic parameters and particular surgical procedure parameters selected by that surgeon. By inserting the key into the system console jack, the system is automatically set up to respond in a familiar way to each surgeon.

For maximum versatility, the console push buttons and potentiometer knobs are programmable. Their functions and response characteristics can be changed to suit the surgeon's needs. An electronic display screen on the console displays the current function of each programmable button and knob as well as other pertinent information. The display screen is self-illuminating so that it can be read easily in darkened operating rooms.

More specifically, the microsurgical control system of the invention is adapted for controlling fluid pressure controlled microsurgical instruments. The term "fluid pressure", unless otherwise specified, includes both positive pressure and negative pressure (vacuum), as well as pneumatic implementations. The microsurgical control system comprises a means for providing fluid pressure couplable to the microsurgical instrument for delivering a fluid pressure signal to the instrument. A manually actuable controller is coupled with the means for providing fluid pressure for adjusting the fluid pressure signal in response to human actuation. A digitally programmed electronic circuit coupled to the controller selectively alters the manner in which the controller responds to human actuation.

Further, in accordance with the invention, the microsurgical control system includes a console and means on the console for connecting to at least one microsurgical instrument. The console has an electronic display screen and a plurality of manually actuable controllers disposed thereon at locations corresponding to predetermined regions of the display screen. The system includes a menu generating means coupled to the display screen for writing predetermined human readable messages at the predetermined regions of the display screen. A procedure control means is coupled to the connecting means for defining and providing a plurality of predetermined and selectable surgical procedures for controlling the instrument. A procedure selection means is coupled to the procedure control means and is responsive to the human actuable controller, for causing the procedure control means to perform a selected one of the plurality of procedures.

Still further in accordance with the invention, the control means includes a means for defining predetermined and selectable surgical procedures. The defining means includes a jack on the console and at least one memory circuit removably connected to the jack, for storing parameters used to define the surgical procedures.

For a more complete understanding of the invention, its objects and advantages, reference may be had to the following specification and to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the microsurgical system of the invention;

FIG. 2 is a front view of the system console showing the front panel layout in greater detail;

FIG. 3 is a system block diagram of the electronic control system of the invention;

FIG. 4 is a detailed schematic diagram illustrating the processor and related components of the electronic control system;

FIG. 5 is a detailed schematic diagram illustrating the reset and watchdog circuits of the electronic control system;

FIG. 6 is a detailed schematic diagram illustrating the system bus structure of the electronic control system;

FIG. 7 is a detailed schematic diagram illustrating the dual UART circuit of the electronic control system;

FIG. 8 is a detailed schematic diagram illustrating the memory circuits of the electronic control system;

FIG. 9 is a detailed schematic diagram illustrating the key memory circuits of the electronic control system;

FIG. 10 is a detailed schematic diagram illustrating the digital potentiometer circuits of the electronic control system;

FIG. 11 is a detailed schematic diagram illustrating the foot controller pedal circuitry of the electronic control system;

FIG. 12 is a detailed schematic diagram illustrating the interrupt request handling circuitry of the electronic control system;

FIG. 13 is a detailed schematic diagram illustrating the video circuitry of the electronic control system;

FIG. 14 is a detailed schematic diagram also illustrating the video circuitry of the electronic control system;

FIGS. 15-17 are detailed schematic diagrams illustrating the analog peripheral control circuitry of the electronic control system; and

FIGS. 18-31 depict various menus displayable on the display screen of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIGS. 1 and 2, a microsurgical control system 10 is provided having a foot pedal assembly 24 according to the present invention. The control system 10 includes a system console 12 which has an upwardly and inwardly sloping front panel 14 and at least one removable access door 254 in one of the side panels. On the front panel 14 is an electronic display screen 16, a plurality of push button switches or tooth sensitive pads 18 and a plurality of "endless" digital potentiometer knobs 20. The push buttons 18 and knobs 20 are actuable by the surgeon or nurse to select various different modes of operations and functions used in various surgical procedures.

The console 12 also includes a cassette eject button 36, an irrigation pitch valve 37, and a power on/off switch 38.

The electronic display screen 16 is controlled by a computer to provide one or more different menus or messages which instruct the operator as to the function of the buttons 18 and knobs 20 for the particular mode selected. The display screen 16 may be conceptually divided into display screen regions 22 with the buttons 18 and knobs 20 being positioned at locations around the periphery of the screen 16 corresponding to the regions 22. By virtue of the location of the buttons 18 and knobs 20 adjacent the screen 16, for example, a message in the upper left-hand corner of the screen 16 is readily understood by the operator as referring to the upper left most button. This arrangement allows the indicated function of each button 18 and knob 20 to be readily changed. The use of an electronic display screen 16 also permits the buttons 18 and knobs 20 to be labeled in virtually any language.

The microsurgical control system 10 is adapted for use with a number of different surgical instruments. As shown in FIG. 1, a fiber optic illumination instrument 214 is coupled to the console 12 via fiber optic cable 212. Also illustrated is a fragmentation emulsification instrument 28 coupled to the console 12 through an electrical cable 30. The instrument 28 is also coupled to a collection container or cassette 100 through an aspiration tube 31. A cutting instrument 32 is also shown which is coupled to the console 12 through tubing 34 and to the cassette 100 through tubing 35. The cutting instrument 32 may be a guillotine cutter for vitrectomy procedures, or it may be a microscissors instrument for proportionate and multiple cutting. However, when the microscissors instrument is used, the instrument is not connected to the cassette 100.

While certain microsurgical instruments have been illustrated in FIG. 1, it will be understood that the microsurgical control system 10 can be used with other similarly equipped instruments. In general, any of the microsurgical instruments are actuated or controlled by fluid pressure (positive pressure or negative pressure). However, it should be appreciated that other suitable types of control signals may be used in the appropriate application.

To provide irrigation/aspiration capabilities, the control system 10 further includes the removable cassette 100 which may be inserted into a cassette slot 102 in the console 12. The cassette 100 has a passageway opening 148 to which an aspiration tube from an aspiration instrument may be connected. The console 12 also includes a plurality of couplers 40 to which surgical instruments described above may be attached. Above each coupler 40 is a light emitting diode 42 which is illuminated when the instrument connected to the associated coupler 40 is activated. To store the operating parameters of a particular microsurgical operation, the control system 10 electrically communicates with a digitally encoded memory key K21. The memory key K21 includes an integrated memory circuit which stores the operating parameters for a particular surgical procedure. The console 12 receives the key K21 through a slot J21. Suitable types of memory keys K21 are commercially manufactured by Data Key Inc., Burnsville, MN. However, it should be appreciated that other suitable means for accessing specifically assigned memory locations may be used in the appropriate application.

A further description of the control system may also be found in the following commonly owned patent applications which were filed on even date herewith, and which are hereby incorporated by reference: Scheller, et al U.S. patent application Ser. No. 982,265, entitled "Collection Container For Ophthalmic Surgical Instruments"; Scheller, et al U.S. patent application Ser. No. 927,827, entitled "Illumination System For Fiber Optic Lighting Instruments"; and Scheller U.S. patent application Ser. No. 927,807, entitled "Foot Pedal Assembly For Ophthalmic Surgical Instrument".

Referring now to FIG. 3, a system overview of the microsurgical control system will be presented. The control system of the presently preferred embodiment centers around a microprocessor 310, such as a Motorola 6809. Connected to the reset terminal of the microprocessor is a reset logic circuit 312 and watchdog circuit 314. Reset logic circuit 313 performs the power on reset and manual reset functions, while the watchdog circuit monitors the operation of the microprocessor and causes it to be reset in the event it should enter an endless software loop or wait state. The details of the reset logic and watchdog circuits will be discussed below in connection with FIG. 5.

Microprocessor 310 communicates with a processor address bus PAn and with a processor data bus PDn. In the presently preferred embodiment, the address and data bus structure is divided into two parts, one part for addressing the kernel of the machine and the other part for addressing the higher level system components. The kernel provides most of the peripheral device-independent functions and gives the control system its default or start up characteristics. The higher level system portion gives the control system the capability of being programmed to handle a variety of different surgical procedures with response characteristics tailor fit to a particular surgeon. As seen in FIG. 3, the processor address bus PAn and the processor data bus PDn both branch forming two portions. The resulting four branches are buffered in buffers 316, 318, 320 and 322. Buffers 316 and 318 address the kernel of the machine on address bus An and data bus Dn. Buffers 320 and 322 address the system portion of the machine on address bus BAnSYS and on data bus BDnSYS.

In order to select whether the kernel portion or the system portion is to be addressed by microprocessor 310 and in order to maintain control over the direction of data flow, a buffer control circuit 324 is provided. Buffer control circuit 324 is responsive to address lines A11-A15 of address bus An. It provides a plurality of control signals coupled to buffers 318 and 322 for selecting which of the two data buses (Dn or BDnSYS) are active and for controlling the direction of data flow. Thus by addressing buffer control circuit 324, microprocessor 310 can selectively address either the kernel portion or the system portion of the invention.

The bulk of the kernel appears generally at 326 and includes EPROM 328 and nonvolatile RAM 330. EPROM 328 contains the kernel operating system program instructions while nonvolatile RAM 330 contains the default data values used to define the system's default operating parameters. Also coupled to the kernel is dual UART (DUART) 332 which provides serial communication with microprocessor 310 via ports A and B. These ports may be accessed in order to monitor the microprocessor machine states during software debugging and programming and may also be used to connect to an external computer system for use in loading updated software into the machine and for testing the system. If desired, either or both of the ports can be connected to modem circuits for remote communication with the system via telephone lines. This feature would permit software updates to be made without requiring the unit to be shipped back to the factory.

Also part of the kernel 326 is a peripheral decoding circuit 334 which is coupled to address bus An and which provides a plurality of board select signals BOARDn and a plurality of chip select signals CSn, which microprocessor 310 can activate to select a particular peripheral controller board or to select a particular peripheral controller chip. These will be discussed more fully below.

The system portion of the invention is illustrated generally at 336. The system portion communicates with the system buses BAnSYS and BDnSYS. Included in the system portion are a plurality of universal memory sites 338 which can contain random access memory chips programmed to contain alternate response characteristics which differ from the default characteristics stored in RAM 330. Also provided is EEROM 340 which is an electrically erasable ROM used to store the calibration arrays for determining the response of the pneumatic systems or fluid pressure controlled systems of the invention. The values stored in EEROM 340 represent calibration values preferably set and stored at the factory. Because an electrically erasable ROM is used, these values can be erased and updated under appropriate software control. In the presently preferred embodiment, this reprogramming is not available to the end user, but would normally be performed by a qualified technician via the serial ports A and B of dual UART 332. The microfiche appendix provides one example of a suitable program which could used in the control console according to the present invention. This microfiche appendix is hereby incorporated by reference.

Each of the universal memory sites 338, as well as EEROM 340, EPROM 328 and nonvolatile RAM 330 include a memory select control input MSn. Control circuit 324, under microprocessor control, provides the memory select signals used to activate a particular memory device. In addition to these memory devices, the invention also has the capability to address a removable memory device which can be removably connected to a jack accessible on the exterior of the system console. This removable memory device or key memory 342 may be programmed by the end user for storing parameters used to define particular surgical procedures and particular response characteristics desired by a given surgeon. Although the key memory devices may be implemented in a variety of different package configurations, the presently preferred configuration is in the form of a removable electronic key. The key has a plurality of electrical contacts connected to a nonvolatile electrically alterable memory chip which is encapsulated in the body of the key. When the key is inserted into the jack on the system console and turned, the encapsulated memory chip is coupled to the key memory space 342 of the system portion of the circuit. The particular parameters and surgical procedures stored in the key memory are then accessible to microprocessor 310 to override the default parameters stored in nonvolatile RAM 330. It should be noted, however, that the key is only necessary to override the default values, and that the system may be operated without the key using the default values.

In order to provide an interface between the human operator and the control system, several human actuable controllers are provided. These controllers include a plurality of "endless" digital potentiometers 20 and associated buffering circuitry 344 to which the front panel potentiometer knobs 20 are connected. In one embodiment according to the present invention, these digital potentiometers are Hewlett Packard Model HEDS7501 controllers. The signals generated by these potentiometers are related to specific operating parameters by the software. Accordingly, it should be that this feature permits multiple uses to be made of these potentiometers for different surgical procedures. As will be seen in connection with FIGS. 18-31, the display screen 16 is used to display an indication of the special operating parameters for these potentiometers.

The digital potentiometers are connected to the system data bus BDnSYS and are selected by activation of certain of the chip select lines (CS2-CS4). The foot controller pedal 24 coupled to foot control circuitry 346 also provides human actuable control via the system data bus. In addition, push buttons 18 likewise provide human actuable control. These buttons are coupled through push button interface circuitry 348 to the system data bus. Like the digital potentiometer circuitry, the foot control circuitry and the push button interface circuitry are selected by certain of the chip select lines. The foot controller is selected by chip select lines CS13-CS15, and the push button circuits are selected by CS8-CS9.

The human actuable controllers, i.e. the digital potentiometers, the foot controller pedal and the push button monitor switches, may be considered as peripheral devices. In addition to these peripheral devices, the microsurgical control system 10 also includes several analog peripheral devices, i.e. the fluid pressure actuated surgical implements. To simplify the illustration in FIG. 3, these analog peripherals and their associated control circuitry have been designated generally by block 350.

The microsurgical control system also includes a video monitor 352 which defines display screen 16 and on which human readable messages are displayed. As will be more fully explained below, monitor 352 displays a series of different menus which identify the current function of each of the monitor switches 18 and digital potentiometers 20. In addition, the menus also provide certain other information to the surgeon, such as the operating parameter values selected by the appropriate rotation of the digital potentiometers. The video monitor is supplied with horizontal and vertical sync signals and a video signal via signal processor circuit 354. Signal processor circuit 354 receives the 10 MHz clock signal from oscillator 356 as well as the vertical and horizontal sync signals from CRT controller 358. Each of the pixel locations on monitor 352 has one or more corresponding memory cell locations within video RAM circuit 360. The video RAM circuit is a dual ported memory circuit which can be directly accessed by both the monitor via the shift register (SR) interface circuit 362 and which may be accessed by the microprocessor via buffer 364. The presently preferred video screen has a 256 by 512 pixel resolution. Data to be displayed on monitor 352 is input through buffer 364 to video RAM 360 during a first half of the microprocessor machine cycle. During the second half of the machine cycle, the data is converted to a video signal and written to the monitor for display. As illustrated in FIG. 3, the monitor circuit defines a separate buffer data bus BDnVID, which is coupled to the system data bus BDnSYS through buffer 366.

Because many of the peripheral devices are interrupt handled devices, a system timer and interrupt request circuit 368 is provided. When a peripheral device needs attention of the microprocessor, it generates an interrupt which is handled by the interrupt request circuit 368, causing the appropriate microprocessor interrupt to be generated. Circuit 368 also generates a system timer which is coupled to a speaker 370 to produce a periodic audible beeping tone. The audible beeping tone is presently tied to the aspiration function. It provides a tone which periodically beeps at a rate proportional to the aspiration rate. The audible beeping tone provides a continuous audible indication of the aspiration rate so that the surgeon does not need to look away from the surgical situs in order to determine the aspiration level.

Having given an overview of the microsurgical control system, a more detailed analysis of the circuit will now be presented.

The detailed schematic diagrams of FIGS. 4-17 have been provided with the customary pin designations where applicable. In these detailed schematic diagrams, many of the interconnecting leads and buses have been omitted for clarity; and it will be understood that the circuits with like pin designations share common signal lines and buses.

Referring now to FIG. 4, microprocessor 310 is illustrated. In FIG. 4, microprocessor 310 is also designated U1. The kernel address buffer 316 comprises two buffer circuits U27 and U28 which may be LS245 integrated circuits. The kernel data buffer 318 is implemented using buffer circuit U2 which may also be a LS245 integrated circuit. The DIR terminal of circuit U2 is responsive to the DIRKER* control signal and the E* terminal is responsive to the SELKER* control signal. The SELKER* control signal selects the kernel data bus as the active bus and the DIRKER* control signal controls the data flow direction. These control signals are generated by the buffer control circuit 324 which includes circuits U9 and U10, both programmable array logic chips, such as PAL16L8 integrated circuits. These circuits are coupled to the A11-A15 address lines and decode these lines to produce the control signals indicated in FIG. 4. Among the control signals provided are memory select signals MSN (MS0-MS7). These signals are used to select which of the memory chips is being accessed by microprocessor 310.

Also illustrated in FIG. 4 is EPROM 328 and nonvolatile RAM 330. These memory circuits are also designated U5 and U6, respectively. EPROM 328 may be a 2764 integrated circuit, while nonvolatile RAM 330 may be an HM6264-15 integrated circuit. As illustrated, EPROM 328 is enabled by MS7 memory select signal while RAM 330 is enabled by the MS0 memory select signal.

Also illustrated in FIG. 4 is peripheral decode circuit 334, which is also designated U7. This circuit may be a PAL20L10 integrated circuit. It provides the function selection and board selection by decoding address lines A4-A15. In addition to providing the BOARDn control signals (BOARD0-BOARD1), U7 also provides several other control signals indicated, including a control signal for operating dual UART 332. In addition to circuit U7, the peripheral decode circuit 334 also comprises circuit U8, shown in FIG. 6. Circuit U8 may be an LS154 integrated circuit which decodes address lines A0-A3 and provides a plurality of chip select signals CSn (CS0-CS15). As illustrated, circuit U8 is enabled by the BOARD0* signal from U7.

Referring now to FIG. 5, the reset logic circuits 312 and watchdog circuit 314 are illustrated. The reset logic circuits provide an output at circuit U43 which is designated MPURST*. This signal is coupled to microprocessor 310 (FIG. 4) to provide a reset signal to the microprocessor. The reset circuits include a power on reset circuit 372 which couples to the reset logic circuit 374. The power on reset circuit provides a reset signal a sufficient time after powerup to ensure that the microprocessor is properly operating. Reset logic circuit 374, in addition to providing the microprocessor reset signal MPURST*, also provides hardware reset signals HDRST and HDRST* for resetting the peripheral devices connected to the system. This arrangement allows the microprocessor to be reset, to change memory banks for effecting different operations, for example, without requiring the hardware reset of the peripheral devices. The reset functions may be instigated by software control or by manually operated reset push buttons. The reset logic circuits 312 include a reset button control logic circuit 376 through which manual reset of both the microprocessor and the system can be accomplished using switches SW1 and SW2.

Watchdog timer circuit 314 is a resettable timer circuit. During normal operation, the microprocessor, acting through control signal WATCHDOGRST*, resets or reinitializes the watchdog circuit every 40 to 50 milliseconds. The watchdog reset control signal WATCHDOGRST* is provided by the dual UART 332, shown in FIG. 7. As long as the watchdog circuit is periodically reinitialized, it will not affect operation of the microprocessor. However, if not reinitialized after approximately 200 to 300 milliseconds, watchdog circuit 314 produces an output signal which causes the microprocessor reset signal MPURST* to be generated.

One purpose of the watchdog circuit is to reset the microprocessor and the system in the event the microprocessor loses program control due to a power surge or dropout. This is implemented by requiring the microprocessor to periodically generate the watchdog reset control signal as one of its many functions. If program control is lost, the microprocessor will not generate this control signal, whereupon the watchdog circuit 314 will cause a reset.

Another use for the watchdog circuit is in switching between memory banks. The control system of the invention employs several memory banks, which are discussed more fully below. These memory banks may be programmed to contain different sets of instructions, operating parameters, and the like. Normally, the microprocessor would operate based on instructions contained in one or more of the memory banks, with the remaining banks containing different instructions held in reserve for other users. For example, the memory banks may be programmed to display operating instructions in a variety of different languages: English, French, German, Japanese and so forth. In order to switch from one bank to another, the microprocessor executes program instruction code which appropriately changes the default memory to be selected. The microprocessor then purposefully fails to reinitialize the watchdog circuit, causing a reset to occur. When the reset occurs, the machine state reinitializes with the newly selected memory bank in place of the previously selected one. Also, if desired, hardware switches or jumpers may be used to determine which memory banks are active upon power up.

Also illustrated in FIG. 5, is the indicator driver circuitry 378 which is used to illuminate the LED indicators 42 above the couplers 40 on the front panel of console 12.

Referring now to FIG. 6, the system address buffers 320 and system data buffer 322 are illustrated. System address buffers 320 are designated U29 and U30 while system data buffer is designated U3. Like the