GB1599869A - Copy reproduction machine with controller self check system - Google Patents

Description

(54) COPY REPRODUCTION MACHINE WITH CONTROLLER SELF CHECK SYSTEM (71) We, XEROX CORPORATION, of Xerox Square, Rochester, New York, United States of America, a corporation organised under the laws of the State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to electrostatographic xerographic type reproduction machines, and more particularly, to an improved control system for such machines.

The advent of higher speed and more complex copiers and reproduction machines has brought with it a corresponding increase in the complexity in the machine control wiring and logic. While this complexity manifests itself in many ways, perhaps the most onerous involves the inflexibility of the typical control logic/wiring systems, because, as can be appreciated, simple unsophisticated machines with relatively simple control logic and wiring can be altered and modified easily to incorporate changes, retrofits, and the like. Servicing and repair of the control logic is also fairly simple. On the other hand, some modern high speed machines, which often include sorters, a document handler, choice of copy size, multiple paper trays, jam protection and the like, have extremely complex logic systems making even the most minor changes and improvements in the control logic difficult, expensive and time-consuming. Servicing or repairing the machine control logic may similarly entail substantial difficulty, time and expense.

The present invention provides a method of verifying transmission of control signals to a controlled element as claimed in the appended claims.

Related other inventions form the subject-matter of our copending applications 23235/78 (serial number 1599868) and 23312/78 (serial number 1599870).

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is a schematic representation of a reproduction apparatus embodying the present invention Fig. 2 is a schematic view showing a paper path and sensors of the apparatus shown in Fig. I; Fig. 3 is an enlarged view showing details of a copy sorter for the apparatus shown in Fig. 1; Fig. 4 is a schematic view showing details of a document handler for the apparatus shown in Fig. 1; Fig. 5 is a block diagram of a controller for the apparatus shown in Fig. 1; Fig. 6 is a block diagram of the controller CPU; Fig. 7a is a block diagram showing a CPU microprocessor input/output connections; Fig. 7b is a timing chart of direct memory access (DMA) read and write cycles; Fig. 8 is a logic schematic of the CPU memory; Fig. 9 is a logic schematic of the CPU memory ready; Figs. 10a and 10b comprise a block diagram of a controller I/O module; Fig. 11 is a logic schematic of a nonvolatile memory power supply; Fig. 12 is a block diagram of an apparatus interface and remote output connections; Fig. 13 is a block diagram of a CPU interface module; Fig. 14 is a block diagram of an apparatus special circuits module; Fig. 15 is a block diagram of a main panel interface module; Fig. 16 is a block diagram of an input matrix module; Fig. 17 is a block diagram of a typical remote; Fig. 18 is a block diagram of a sorter remote; Fig. 19 is a view of a control console for inputting copy run instructions to the apparatus shown in Fig. 1; Fig. 20 is a flow chart illustrating a typical machine state; Fig. 21 is a flow chart of a machine state routine; Fig. 22 is a view showing an event table layout; Fig. 23 is a chart illustrating the relative timing sequences of clock interrupt pulses; Figs. 24a, 24b, 24c are a timing chart of the principal operating components of the host machine in an exemplary copy run; and Fig. 25 is a flow chart showing a memory checksum comparison test routine; Figs. 26a and 26b are the flow charts showing an output driver stuck test routines; Fig. 27 is a flow chart showing a check checker board pattern routine; Figs. 28a and 28b are a flow chart showing a ram address check routine; Fig. 29 is a flow chart showing a nonvolatile memory test routine; Figs. 30a and 30b are flow charts showing an address wrap-around test routine Figs. 31a and 31b are flow charts showing the controller interface refresh test routine; Fig. 32 is a flow chart showing a data transmission to digit display test routine; Figs. 33a and 33b are flow charts showing the data transmission verification to remote modules routine.

Referring particularly to Figures 14 of the drawings, there is shown, in schematic outline, an electrostatic reproduction system or host machine, identified by numeral 10, incorporating the control arrangement of the present invention. To facilitate description, the reproduction system 10 is divided into a main electrostatic xerographic processor 12, sorter 14, document handler 16, and controller 18.

Other processor, sorter and/or document handler types and constructions, and different combinations thereof, are possible.

Processor 12 utilizes a photoreceptor in the form of an endless photoconductive belt 20 supported in generally-triangular configuration by rolls 21, 22, 23. Beltsupporting rolls 21, 22, 23 are in turn rotatably journaled on subframe 24.

In the exemplary processor illustrated, belt 20 comprises a photo-conductive layer of selenium, which is the light-receiving surface and imaging medium, on a conductive substrate.

Suitable biasing means (not shown) are provided on subframe 24 to tension the photoreceptor belt 20 and ensure movement of belt 20 along a prescribed operating path.

Belt-tracking switch 25 monitors movement of belt 20 from side to side. Belt 20 is supported so as to provide a trio of substantially-flat belt runs opposite exposure, developing, and cleaning stations 27, 28, 29 respectfully. To enhance belt flatness at these stations, vacuum platens 30 are provided under belt 20 at each belt run.

Conduits 31 communicate vacuum platens 30 with a vacuum pump 32.

Photoconductive belt 20 moves in the direction indicated by the solid line arrow, drive thereto being effected through roll 21, which in turn is driven by main drive motor 34.

Processor 12 includes a generallyrectangular, horizontal transparent platen 35 on which each original 2 to be copied is disposed. A two- or four-sided illumination assembly, consisting of internal reflectors 36 and flash lamps disposed below and along at least two sides of platen 35, is provided for illuminating the original 2 on platen 35. To retain the original 2 in place on platen 35, and prevent escape of extraneous light from the illumination assembly, a platen cover 35' may be provided.

The light image generated by the illumination system is projected via mirrors 39, 40 and a variable magnification lens assembly 41 onto the photoreceptive belt 20 at the exposure station 27. Reversible motor 43 is provided to move the main lens and add-on lens elements that comprise the lens assembly 41 to different predetermined positions and combinations to provide the preselected image sizes corresponding to push button selectors 818, 819, 820 on operator module 800. (See Figure 19) Sensors 116, 117, 118 signal the present disposition of lens assembly 41. Exposure of the previously-charged belt 20 selectively discharges the photoconductive belt to produce on belt 20 an electrostatic latent image of the original 2. To prepare belt 20 for imaging, belt 20 is uniformly charged to a preselected level by charge corotron 42 upstream of the exposure station 27.

To prevent development of charged but unwanted image areas, erase lamps 44, 45 are provided. Lamp 44, which is referred to herein as the pitch fadeout lamp, is supported in transverse relationship to belt 20, lamp 44 extending across substantially the entire width of belt 20 to erase (i.e.

discharge) areas of belt 20 before the first image, between successive images and after the last image. Lamps 45, which are referred to herein as edge fadeout lamps, serve to erase areas bordering each side of the images.

Referring to Fig. 1, magnetic brush rolls 50 are provided in a developer housing 51 at developing station 28. Housing 51 is pivotally supported adjacent the lower end thereof with interlock switch 52 to sense disposition of housing 51 in operative position adjacent belt 20. The bottom of housing 51 forms a sump within which a supply of developing material is contained.

A rotatable auger 54 in the sump serves to mix the developing material and bring the material into operative relationship with the lowermost of the magnetic brush rolls 50.

As will be understood by those skilled in the art, the electrostatically attractable developing material commonly used in magnetic brush developing apparatus of the type shown comprises a pigmented resinous powder, referred to as toner, and larger granular beads referred to as carrier. To provide the necessary magnetic properties, the carrier is comprised of a magnetizable material such as steel. By virtue of the magnetic fields established by developing rolls 50 and the interrelationship therebetween, a blanket of developing material is formed along the surfaces of developing rolls 50 adjacent the belt 20 and extending from one roll to another. Toner is attracted to the electrostatic latent image from the carrier bristles to produce a visible powder image on the surface of belt 20.

Developing material is returned to the upper portion of developer housing 51 for reuse and is accomplished by utilizing a photocell 62 which monitors the level of developing material in housing 51 and a photocell lamp 62' spaced opposite to the photocell 62 in cooperative relationship therewith.

To discharge toner from container 67, rotatable dispensing roll 68 is provided in the inlet to developer housing 51. Motor 69 drives roll 68. When fresh toner is required, as determined by the signal from photocell 65, controller 18 actuates motor 69 to turn roll 68 for a timed interval. The rotating roll 68, which is comprised of a relatively-porous sponge-like material, carriers toner particles thereon into developer housing 51 where it is discharged. Pre-transfer corotron 70 and lamp 71 are provided downstream of magnetic brush rolls 50 to regulate developed image charges before transfer.

A magnetic pick-off roll 72 is rotatably supported opposite belt 20 downstream of pretransfer lamp 71, roll 72 serving to scavenge leftover carrier from belt 20 preparatory to transfer of the developed image to the copy sheet 3.

Referring to Fig. 2, to transfer developed images from belt 20 to the copy sheets 3, a transfer roll 75 is provided. Transfer roll 75, which forms part of the copy sheet feed path, is rotatably supported within a transfer roll housing opposite belt-support roll 21.

Housing 76 is pivotably mounted at 76' to permit the transfer roll assembly to be moved into and out of operative relationship with belt 20. A transfer roll cleaning brush 77 is rotatably journalled in transfer roll housing 76 with the brush periphery in contact with transfer roll 90.

Transfer roll 75 is driven through contact with belt 20 while cleaning brush 77 is coupled to main drive motor 34. To remove toner, housing 76 is connected through conduit 78 with vacuum pump 81. To facilitate and control transfer of the developed images from belt 20 to the copy sheets 3, a suitable electrical bias is applied to transfer roll 75.

To facilitate separation of the copy sheets 3 from belt 20 following transfer of developed images, a detack corotron 82 is provided. Corotron 82 generates a charge designed to neutralize or reduce the charges tending to retain the copy sheet on belt 20.

Corotron 82 is supported on transfer roll housing 76 opposite belt 20 and downstream of transfer roll 75.

Referring to Fig. 1, to prepare belt 20 for cleaning, residual charges on belt 20 are removed by discharge lamp 84 and preclean corotron 94. A cleaning brush 85, rotatably supported within an evacuated semicircular shaped brush housing 86 at cleaning station 29, serves to remove residual developer from belt 20. Motor 95 drives brush 85, brush 85 turning in a direction opposite that of belt 20.

To obviate the danger of copy sheets remaining on belt 20 and becoming entangled with the belt-cleaning mechanism, a deflector 96 is provided upstream of cleaning brush 85. Deflector 96, which is pivotally supported on the brush housing 86, is operated by solenoid 97. In the normal, or 'off', position, deflector 96 is spaced from belt 20 (the solid line position shown in the drawings). Energization of solenoid 97 pivots deflector 96 downwardly to bring the deflector leading edge into close proximity to belt 20.

Sensors 98, 99 are provided on each side of deflector 96 for sensing the presence of copy material on belt 20. A signal output from upstream sensor 98 triggers solenoid 97 to pivot deflector 96 into position to intercept the copy sheet on belt 20. The signal from sensor 98 also initiates a system shutdown cycle (mis-strip jam) wherein the various operating components are, within a prescribed time, brought to a stop. The interval permits any copy sheet present in fuser 150 to be removed, sheet trap solenoid 158 (Fig. 2) having been actuated to prevent the next copy sheet from entering fuser 150 and becoming trapped therein. The signal from sensor 99, indicating failure of deflector 96 to intercept or remove the copy sheet from belt 20, triggers an immediate or hard stop (sheet - on - belt jam) of the processor. In such instances the power to drive motor 34 is interrupted to bring belt 20 and the other components driven therefrom to an immediate stop.

Referring particularly to Figures 1 and 2, copy sheets 3 comprise precut paper sheets supplied from either main or auxiliary paper trays 100, 102. Each paper tray has a platform or base 103 for supporting in stacklike fashion a quantity of sheets. The tray platforms 103 are supported for vertical up and down movement by motors 105, 106.

Side guide pairs 107, in each tray 100, 102 delimit the tray side boundaries, the guide pairs being adjustable toward and away from one another in accommodation of different size sheets. Sensors 108, 109 respond to the position of each side guide pair 107, the output of sensors 108, 109 serving to regulate operation of edge fadeout lamps 45 and fuser cooling valve 171. Lower limit switches 110 on each tray prevent overtravel of the tray platform in a downward direction.

To advance the sheets 3 from either main or auxiliary tray 100, 102, main and auxiliary sheet feeders 120, 121 are provided. Feeders 120, 121 each includes a nudger roll 123 to engage and advance the topmost sheet in the paper tray forward into the nip formed by a feed belt 124 and retard roll 125.

Retard rolls 125, which are driven at a extremely low speed by motor 126, cooperate with feed belts 124 to restrict feeding of sheets from trays 100, 102 to one sheet at a time.

Main transport 140 extends from main paper tray 100 to a point slightly upstream of the nip formed by photoconductive belt 20 and transfer roll 75. Transport 140 is driven from main motor 34. To register sheets 3 with the images developed on belt 20, sheet register fingers 141 are provided, fingers 141 being arranged to move into and out of the path of the sheets on transport 140 once each revolution. Registration fingers 141 are driven from main motor 34 through electromagnetic clutch 145. A timing or reset switch 146 is set once on each revolution of sheet register fingers 141.

Sensor 139 monitors transport 140 for jams.

Auxiliary transport 147 extends from auxiliary tray 102 to main transport 140 at a point upstream of sheet register fingers 141.

Transport 147 is driven from motor 34.

The image-bearing sheets leaving the nip formed by photoconductive belt 20 and transfer roll 75 are picked off by belts 155 of the leading edge of vacuum transport 149.

Belts 155, which are perforated for the admission of vacuum therethrough, ride on forward roller pair 148 and rear roll 153. A pair of internal vacuum plenums 151, 154 is provided, the leading plenum 154 cooperating with belts 155 to pick up the sheets leaving the belt/transfer roll nip.

Transport 149 conveys the image bearing sheets to fuser 150. Vacuum conduits 147, 156 communicate plenums 151, 154 with vacuum pumps 152, 152'. A pressure sensor 157 monitors operation of vacuum pump !52. Sensor 144 monitors transport 149 for jams.

Following fuser 150, the sheet is carried by post fuser transport 180 to either discharge transport 181 or, where duplex or two-sided copies are desired, to return transport 182. Sheet sensor 183 monitors passage of the sheets from fuser 150.

Transports 180, 181 are driven from main motor 34. Sensor 181' monitors transport 181 for jams. Suitable retaining means may be provided to retain the sheets on transports 180, 181.

A deflector 184, when extended, directs sheets on transport 180 onto conveyor roll 185 and into chute 186 leading to return transport 182. Solenoid 179, when energized, raises defector 184 into the sheet path. Return transport 182 carries the sheets back to auxiliary tray 102. Sensor 189 monitors transport 182 for jams. The forward stop 187 of tray 102 is supported for oscillating movement. Motor 188 drives stop 187 back and forth to tap sheets returned to auxiliary tray 102 into alignment for refeeding.

To invert duplex copy sheets following fusing of the second or duplex image, a displaceable sheet stop 190 is provided adjacent the discharge end of chute 186.

Stop 190 is pivotally supported for swinging movement into and out of chute lug6.

Solenoid 191 is provided to move stop 190 selectively into or out of chute 186. Pinch roll pairs 192, 193 serve to draw the sheet trapped in chute 186 by stop 190 and carry the sheet forward onto discharge transport 181.

Output tray 195 receives unsorted copies.

Transport 196 (a portion of which is wrapped around a turn around roll 197) serves to carry the finished copies to tray 195. Sensor 194 monitors transport 196 for jams. To route copies into output tray 195, a deflector 198 is provided. Deflector solenoid 199, when energized, turns deflector 198 to intercept sheets on conveyor 181 and route the sheets onto conveyor 196.

When output tray 195 is not used, the sheets are carried by conveyor 181 to sorter 14.

Referring particularly to Fig. 3, sorter 14 comprises upper and lower bin arrays 210, 211. Each bin array 210, 211 consists of series of spaced downwardly inclined trays 212, forming a series of individual bins 213 for receipt of finished copies 3'. Conveyors 214 along the top of each bin array, cooperate with idler rolls 152 adjacent the inlet to each bin to transport the copies into juxtaposition with the bins. Individual deflectors 216 at each bin cooperate, when depressed, with the adjoining idler roll 215 to turn the copies into the bin associated therewith. An operating solenoid 217 is provided for each deflector.

A driven roll pair 218 is provided at the inlet to sorter 14. A generally vertical conveyor 219 serves to bring copies 3' to the upper bin array 210. Entrance deflector 220 routes the copies selectively to either the upper or lower bin array 210, 211 respectively. Solenoid 221 operates deflector 220.

Motor 222 is provided for each bin array to drive the conveyors 214 and 219 of upper bin array 210 and conveyor 214 of lower bin array 211. Roll pair 218 is drivingly coupled to both motors.

To detect entry of copies 3' in the individual bins 213, a photoelectric type sensor 225, 226 is provided at one end of each bin array 210, 211 respectively. Sensor lamps 225', 226' are disposed adjacent the other end of the bin array. To detect the presence of copies in the bins 213, a second set of photoelectric type sensors 227, 228 is provided for each bin array, on a level with a tray cutout (not shown). Reference lamps 227', 228' are disposed opposite sensors 227, 228.

Referring particularly to Fig. 4, document handler 16 includes a tray 233 into which originals or documents 2 to be copied are placed by the operator, following which a cover (not shown) is closed. A movable bail or separator 235, driven in an oscillatory path from motor 236 through a solenoidoperated one-revolution clutch 238, is provided to maintain document separation.

A document feed belt 239 is supported on drive and idler rolls 240, 241 and kicker roll 242 under tray 233, tray 233 being suitably apertured to permit the belt surface to project therewithin. Feedbelt 239 is driven by motor 236 through electromagnetic clutch 244. Guide 245, disposed near the discharge end of feed belt 239, cooperates with belt 239 to form a nip between which the documents pass.

A photoelectric type sensor 246 is disposed adjacent the discharge end of belt 239. Sensor 246 responds on failure of a document to feed within a predetermined interval to actuate solenoid-operated clutch 248, which raises kicker roll 242 and increases the surface area of feed belt 239 in contact with the documents. Another sensor 259 located underneath tray 233 provides an output signal when the last document 2 of each set has left the tray 233.

Document guides 250 route the document fed from tray 233 via roll pair 251, 252 to platen 35. Roll 251 is drivingly coupled to motor 236 through electromagnetic clutch 244. Contact of roll 251 with roll 252 turns roll 252.

Roll pair 260, 261 at the entrance to platen 35 advance the document onto platen 35, roll 260 being driven through electromagnetic clutch 262 in the forward direction. Contact of roll 260 with roll 261 turns roll 261 in the document feeding direction.

To locate the document in predetermined position on platen 35, a register 273 is provided at the platen inlet for engagement with the document trailing edge. For this purpose, control of platen belt 270 is such that following transporting of the document onto plate 35 and beyond register 273, belt 270 is reversed to carry the document backwards against register 273.

To remove the document from platen 35 following copying, register 273 is retracted to an inoperative position. Solenoid 274 is provided for moving register 273.

A document deflector 275 is provided to route the document leaving platen 35 into return chute 276. For this purpose, platen belt 270 and pinch roll pair 260, 261 are reversed through engagement of clutch 265.

Discharge roll pair 278, driven by motor 236, carry the returning document into tray 233.

To monitor movement of the documents in document handler 16 and detect jams and other malfunctions, photoelectric type sensors 246 and 280, 281 and 282 are disposed along the document routes.

To align documents 2 returned to tray 233, a document patter 284 is provided adjacent one end of tray 233. Patter 284 is oscillated by motor 285.

To provide the requisite operational synchronization between host machine 10 and controller 18 as will appear, processor or machine clock 202 is provided. Referring particularly to Fig. 1, clock 202 comprises a toothed disc 203 drivingly supported on the output shaft of main drive motor 34. A photoelectric type signal generator 204 is disposed astride the path followed by the toothed rim of disc 203, generator 204 producing, whenever drive motor 34 is energized, a pulse-like signal output at a frequency correlated with the speed of motor 34, and the machine components driven therefrom.

As described, a second machine clock, termed a pitch reset clock 138 herein, and comprising timing switch 146 is provided.

Switch 146 cooperates with sheet register fingers 141 to generate an output pulse once each revolution of fingers 141. As will appear, the pulse-like output of the pitch reset clock is used to reset or resynchronize controller 18 with host machine 10.

A real time clock, such as clock 552 of Fig. 6, is utilized to control internal operations of the controller 18 as is known in the art.

Referring to Fig. 5, controller 18 includes a central processor unit (CPU) module 500, input/output (I/O) module 502, and interface 504. Address, data and control buses 507, 508, 509 respectively operatively couple CPU module 500 and I/O module 502, which are disposed within a shield 518 to prevent noise interference.

Interface 504 couples I/O module 502 with special circuits module 522, input matrix module 524, and main panel interface module 526. Module 504 also couples I/O module 502 to operating sections of the machine, namely, document handler section 530, input section 532, sorter section 534 and processor sections 536, 538. A spare section 540, which may be used for monitoring operation of the host machine, or which may be later utilized to control other devices, is provided.

Referring to Figs. 6 and 7a CPU module 500 comprises a processor 542, such as an Intel 8080 microprocessor manufactured by Intel Corporation, Santa Clara, California, 16K read-only memory (herein ROM) and 2K random access memory (herein RAM) sections 545, 546, memory ready section 548, power regulator section 550, and onboard clock 552. Bipolar tri-state buffers 510, 511 in address and data buses 507, 508 disable the bus on a direct memory access (DMA) signal (HOLDA) as will appear.

While the capacity of memory sections 545, 546 are indicated throughout as being 16K and 2K respectively, other memory sizes may be used.

Referring to Figure 8, the memory bytes in ROM section 545 are implemented by address signals (Ao-A15) from processor 542, selection being effected by 3-to-8 decode chip 560 controlling chip select 1 (CS-1) and a one-bit selection (A 13) controlling chip select 2 (CS-2). The most significant address bits (A14, A 15) select the first 16K of the total 64 bytes of the addressing space. The memory bytes in RAM section 546 are implemented by address signals (Ao-A15) through selector circuit 561. Address bit A 10 serves to select the memory bank, while the remaining five most significant bits (A11--A15) select the last 2 K bytes out of the 64K bytes of addressing space. RAM memory section 546 includes a 40 bit output buffer, the output of which is tied together with the output from ROM memory section 545 and goes to tri-state buffer 562 to drive data bus 508. Buffer 562 is enabled when either memory section 545 or 546 is being addressed and either a (MEM READ) or DMA (HOLD A) memory request exists.

An enabling signal (MEMEN) is provided from the machine control or service panel (not shown) which is used to permit disabling of buffer 562 during servicing of CPU module 500. Write control comes from either processor 542 (MEM WRITE) or from DMA (HOLD A) control. Tri-state buffers 563 permit refresh control 605 of I/O module 502 to access MEM READ and MEM WRITE control channels directly on a DMA signal (HOLD A) from processor 542, as will appear.

Referring to Figure 9, memory-ready section 548 provides a READY signal to processor 542. A binary counter 566, which is initialized by a SYNC signal (0), to a prewired count as determined by input circuitry 567, counts up at a predetermined rate. At the maximum count, the output at gate 568 comes true, stopping the counter 566. If the cycle is a memory request (MEM REQ) and the memory location is on board as determined by the signal (MEM HERE) to tri-state buffer 569, a READY signal is sent to processor 542. Tri-state buffer 570 in MEM REQ line permits refresh control 605 of I/O Module 502 to access the MEM REQ channel directly on a DMA signal (HOLD A) from processor 542, as will appear.

Referring to Figs. 7b 8, and 9, and the DMA timing chart (Fig. 7b) data transfer from RAM section 546 to host machine 10 is effected through direct memory access (DMA), as will appear. To initiate DMA, a signal (HOLD) is generated by refresh control 605 (Fig. 23a). On acceptance, processor 542 generates a signal HOLD ACKNOWLEDGE (HOLD A) which works through tri-state buffers 510, 511 and through buffers 563 and 570 to release address bus 507, data bus 508 and MEM READ, MEM WRITE, and MEM REQ channels (Figs. 8, 9) to refresh control 605 of I/O module 502.

Referring to Figure 10, I/O module 502 interfaces with CPU module 500 through bidirectional address, data and control buses 507, 508, 509. I/O module 502 appears to CPU module 500 as a memory portion. Data transfers between CPU and I/O modules 500, 502, and commands to I/O module 502 except for output refresh, are controlled by memory reference instructions executed by CPU module 500. Output refresh, which is initiated by one of several uniquely-decoded memory reference commands, enables direct memory access (DMA) by I/O module 502 to RAM section 546.

I/O module 502 includes matrix input select 604 (through which inputs from the host machine 10, are received), refresh control 605, non-volatile (NV) memory 610, interrupt control 612, watch dog timer and failure flag 614 and clock 570.

A function decode section 601 receives and interprets commands from CPU section 500 by decoding information on address bus 507 along with control signals from processor 542 on control bus 509. On command, decode section 601 generates control s

A logic signal (INHIBIT RESET) prevents the CPU module 500 from being reset during the NV memory write cycle interval, so that any write operation in progress will be completed before the system is shut down.

For tasks that require frequent servicing, high speed response to external events, or synchronization with the operation of host machine 10, a multiple interrupt system is provided. These comprise machine-based interrupts, herein referred to as pitch reset interrupt and the machine interrupt, as well as a third clock driven interrupt, the real time interrupt.

Referring particularly to Fig. 10(a), the highest priority interrupt signal, pitch reset signal 640, is generated by the signal output of pitch reset clock 138. The clock signal is fed via optical isolator 645 and digital filter 646 to edge trigger flip flop 647.

The second highest priority interrupt signal, machine clock signal 641, is sent directly from machine clock 202 through isolation transformer 648 to a phase-locked loop 649. Loop 649, which serves as bandpath filter and signal conditioner, sends a square wave signal to edge trigger flip flop 651. The second signal output (lock) serves to indicate whether loop 649 is locked onto a valid signal input or not.

The lowest priority interrupt signal, real time clock signal 643, is generated by register 621, which is loaded and stored by memory reference instructions from CPU module 500 and which is decremented by a clock signal in line 643, which may be derived from I/O module clock 570. On the register count reaching zero, register 621 sends an interrupt signal to edge trigger flip flop 656. A spare interrupt 642 is also provided.

Setting of one or more of the edge trigger flip flops 647, 651, 654, 656 by the interrupt signals 640, 641, 642, 643 generates a signal (INT) via priority chip 659 to processor 542 of CPU module 500. On acknowledgement, processor 542 issues a signal (INTA) transferring the status of the edge trigger flip flops 647, 651, 654, 656 to a four-bit latch 660 to generate an interrupt instruction code (RESTART) onto the data bus 508.

Each interrupt is assigned a unique RESTART instruction code. Should an interrupt of higher priority be triggered, a new interrupt signal (INT) and RESTART instruction code are generated, resulting in a nesting of interrupt software routines whenever the interrupt recognition circuitry is enabled within the CPU 500.

Priority chip 659 serves to establish a handling priority in the event of simultaneous interrupt signals in accordance with the priority schedule described.

Once triggered, the edge trigger flip flop 647, 651, 654 or 656 must be reset in order to capture the next occurrence of the interrupt associated therewith. Each interrupt subroutine serves, in addition to performing the functions programmed, to reset the flip flops (through the writing of a coded byte in a uniquely selected address) and to re-enable the interrupt (through execution of a re-enabling instruction).

Until re-enabled, initiation of a second interrupt is precluded while the first interrupt is in progress.

Lines 658 permit interrupt status to be interrogated by CPU module 500 on a memory reference instruction.

CPU interface module 504 interfaces I/O module 502 with the host machine 10 and transmits operating data stored in ram section 546 to the machine. Referring particularly to Fig. 12 and 13, data and address information are inputted to module 504 through suitable means, such as optical type couplers 700 which convert the information to single-ended logic levels.

Data in bus 508, on a signal from refresh control 605 in line 607 (LOAD), are clocked into module 546 at the reference clock rate in line 574 parallel-by-bit, serial-by-byte for a preset byte length, with each data bit of each successive byte being clocked into a separate data channel DO--D7. As best seen in Fig. 12, each data channel DO--D7 has an assigned output function, with data channel DO being used for operating the front panel lamps 830 in the digital display, (See Fig.

19), data channel Dl for special circuits module 522 and remaining data channels D2-D7 allocated to the host machine operating sections 530, 532, 534, 536, 538 and 540. Portions of data channels Dl-D7 have bits reserved for front panel lamps and digital display.

Since the bit capacity of the data channels D2-D7 is limited, a bit buffer 703 is preferably provided to catch any bit overflow in data channels D2-D7.

Inasmuch as the machine output sections 530, 532, 534, 536, 538 and 540 are electrically a long distance away, i.e.

remote, from CPU interface module 504, and-the environment is electrically "noisy".

the data stream in channels D2--D7 is transmitted to remote sections 530, 532, 534, 536, 538 and 540 via a shielded twisted pair 704. By this arrangement, induced noise appears as a differential input to both lines and is rejected. The associated clock signal for the data is also transmitted over line 704 with the shielded line carrying the return signal currents for both data and clock signals.

Data in channel D1 destined for special circuits module 522 are inputted to shift register type storage circuitry 705 for transmittal to module 522. Data are also inputted to main panel interface module 526. Address information in bus 507 is converted to single-ended output by couplers 700 and transmitted to input matrix module 524 to address host machine inputs.

CPU interface module 504 includes fault detector circuitry 706 for monitoring both faults occurring in host machine 10 and faults or failures along the buses, the latter normally comprising a low voltage level or failure in one of the system power lines.

Machine faults may comprise a fault in CPU module 500, a belt mistrack signal, a door open as responded to by conventional cover interlock sensors (not shown), a fuser overtemperature signal, etc. In the event of a bus fault, a reset signal (RESET) is generated automatically in line 709 to CPU module 500 (see Figs. 6 and 7) until the fault is removed. In the event of a machine fault, a signal is generated by the CPU in line 710 to actuate a suitable relay (not shown) controlling power to all or a portion of host machine 10. A load-disabling signal (LOAD DISBL) is inputted to optical couplers 700 via line 708 in the event of a fault in CPU module 500 to terminate input of data to host machine 10. Other fault conditions are monitored by the software background program. In the event of a fault, a signal is generated in line 711 to the digital display on control console 800 (via main panel interface module 526) signifying a fault.

Referrring particularly to Figs. 12 and 14, special circuitx module 522 comprises a collection of relatively-independent circuits for either monitoring operations of and/or driving various elements of host machine 10. Module 522 incorporates suitable circuitry 712 for amplifying the output of sensors 225, 226, 227, 228 and 280, 281, 282 of sorter 14 and document handler 16 respectively; circuitry 713 for operating fuser release clutch 159: and circuitry 714 for operating main and auxiliary paper tray feed roll clutches 130, 131 and document handler feed clutch 244.

Additlonally, fuser detection circuitry 715 monitors temperature conditions of fuser 150 as responded to by sensor 174. On overheating of fuser 150, a signal (FUS-OT) is generated to turn heater 163 off, actuate clutch 159 to separate fusing and pressure rolls 160, 161: trigger trap solenoid 158 to prevent entrance of the next copy sheet into fuser 150, and initiate a shutdown of host machine 10. Circuitry 715 also cycles fuser heater 163 to maintain fuser 150 at proper operating temperatures and signals (FUS RDUT) host machine 10 when fuser 150 is ready for operation.

Circuitry 716 provides closed loop control over sensor 98 which responds to the presence of a copy sheet 3 on belt 20. On a signal from sensor 98, solenoid 97 is triggered to bring deflector 96 into intercepting position adjacent belt 20. At the same time, a backup timer (not shown) is actuated. If the sheet is lifted from the belt 20 by deflector 96 within the time allotted, a signal from sensor 99 disables the timer and a misstrip type jam condition of host machine 10 is declared and the machine is stopped. If the signal from sensor 99 is not received within the allotted time, a sheet-on-selenium (SOS) type jam is declared and an immediate machine stop is effected.

Circuitry 718 controls the position of (and hence the image reduction effected by) the various optical elements that comprise main lens 41 in response to the reduction mode selected by the operator and the signal inputs from lens position responsive sensors 116, 117, 118. The signal output of circuitry 718 serves to operate lens drive motor 43 as required to place the optical elements of lens 41 in proper position to effect the image reduction programmed by the operator.

Referring to Fig. 15, input matrix module 524 provides analog gates 719 for receiving data from the various host machine sensors and inputs (i.e. sheet sensors 135, 136; pressure sensor 157; etc), module 524 serving to convert the signal input to a byteoriented output for transmittal to I/O module 502 under control of input matrix select 604. The byte output to module 524 is selected by address information inputted on bus 507 and decoded on module 524.

Conversion matrix 720, which may comprise a diode array, converts the input logic signals of "0" to logic "1" true. Data from input matrix module 524 is transmitted via optical isolators 721 and input matrix select 604 of I/O module 502 to CPU module 500.

Referring particularly to Fig. 16, main panel interface module 526 serves as interface between CPU interface module 504 and operator control console 800 for display purposes and as interface between input matrix module 524 and the console switches. As described, data channels D0 D7 have data bits in each channel associated with the control console digital display or lamps. These data are clocked into buffer circuitry 723 and from there, for digital display, data in channels D1--D7 are put in to multiplexer 724. Multiplexer 724 selectively multiplexes the data to HEX to 7 segment converter 725. Software-controlled output drivers 726 are provided for each digit which enable the proper display digit in response to the data output of converter 725. This also provides blanking control for leading zero suppression or inter-digit suppression.

Buffer circuitry 723 also enables through anode logic 728 the common digit anode drive. The signal (LOAD) to latch and lamp driver control circuit 729 regulates the length of the display cycle.

For console lamps 830, data in channel DO are clocked to shift register 727 whose output is connected by drivers to the console lamps. Access by input matrix module 524 to the console switches and keyboard is through main panel interface module 526.

The machine output sections 530, 532, 534, 536, 538, 540 are interfaced with I/O module 502 by CPU interface module 504.

At each interrupt/refresh cycle, data is outputted to sections 530, 532, 534, 536, 538, 540 at the clock signal rate in line 574 over data -channels D2, D3, D4, D5, D6, D7 respectively.

Referring to Fig. 17, wherein a typical output section i.e. document handler section 530 is shown, data input to section 530 are stored in shift register/latch circuit combination 740, 741 pending output to the individual drivers 742 associated with each machine component. Preferably d.c.

isolation between the output sections is maintained by the use of transformercoupled differential outputs and input for both data and clock signals and a shielded twisted conductor pair. Due to transformer coupling, the data must be restored to a d.c.

waveform. For this purpose, control recovery circuitry 744, which may comprise an inverting/non-inverting digital comparator pair and output latch, is provided.

The LOAD signal serves to lockout input of data to latches 741 while new data are being clocked into shift register 740.

Removal of the LOAD signal enables commutation of the fresh data to latches 741. The LOAD signal also serves to start timer 745 which imposes a maximum time limit within which a refresh period (initiated by refresh control 605) must occur. If refresh does not occur within the prescribed time limit, timer 745 generates a signal (RESET) which sets shift register 740 to zero.

With the exception of sorter section 534 discussed below, output sections 532, 536, 538 and 540 are substantially identical to document handler section 530.

Referring to Fig. 18, wherein like numbers refer to like parts, to provide capacity for driving the sorter deflector solenoids 221, a decode matrix arrangement, consisting of a prom encoder 750 controlling a pair of decoders 751, 752, is provided. The output of decoders 751, 752 drive the sorter solenoids 221 of upper and lower bin arrays 210, 211 respectively. Data are input to encoder 750 by means of shift register 754.

Referring now to Fig. 19, control console 800 serves to enable the operator to program host machine 10 to perform the copy run or runs desired. At the same time, various indicators on console 800 reflect the operational condition of machine 10.

Console 800 includes a bezel housing 802 suitably supported on host machine 10 at a convenient point with decorative front or face panel 803 on which the various machine programming buttons and indicators appear. Programming buttons include power on/off buttons 804, start print (PRINT) buttons 805, stop print (STOP) button 806 and keyboard copy quantity selector 808. A series of feature select buttons, consisting of auxiliary paper tray button 810, two-sided copy button 811, copy lighter button 814, and copy darker button 815, is provided.

Additionally, image size selector buttons 818, 819, 820; multiple or single document select buttons 822, 823 for operation of document handler 16; and sorter sets or stacks buttons 825, 826, are provided. An on/off service selector 828 is also provided for activation during machine servicing.

Indicators comprise program display lamps 830 and displays such as READY, WAIT, SIDE 1, SIDE 2, ADD PAPER, CHECK STATUS PANEL, PRESS FAULT CODE, QUANTITY COMPLETED, CHECK DOORS, UNLOAD AUX TRAY, CHECK DOCUMENT PATH, CHECK PAPER PATH, JOB INCOMPLETE and UNLOAD SORTER. Other display information may be envisioned.

As will appear, host machine 10 is convenient!y divided into the number of operational states. The machine control program is divided into background routines and foreground routines, with operational control normally residing in the background routine or routines appropriate to the particular machine state then in effect. The output buffer 546' of RAM memory section 546 is used to transfer/refresh control data to the various remote locations in host machine 10, control data from both background and foreground routines being input to buffer 546' for subsequent transmittal to host machine 10. Transmittal/refresh of control data presently in output buffer 546' is effected through direct memory access (DMA) under the aegis of a machine clock interrupt routine.

Foreground routine control data, which include a run event table built in response to the particular copy run or runs programmed, are transferred to output buffer 546' by means of a multiple prioritized interrupt system wherein the background routine in process is temporarily interrupted while fresh foreground routine control data are input to buffer 546', following which the interrupted background routine is resumed.

The operating program for host machine 10 is divided into a collection of foreground tasks, some of which are driven by the several interrupt routines, and background or non-interrupt routines. Foreground tasks are tasks that generally require frequent servicing, high speed response, or synchronization with the host machine 10.

Background routines are related to the state of host machine 10, different background routines being performed with different machine states. A single background software control program (STCK), composed of specific sub-programs associated with the principal operating states of host machine 10, is provided. A byte called STATE contains a number indicative of the current operating state of host machine 10. The machine STATES are as follows: State Control No. Machine State Subr.

0 Software Initialize INIT I System Not Ready NRDY 2 System Ready RDY 3 Print PRINT 4 System Running, RUNNPRT Not Print 5 Servlce TECHREP Referring to Figure 20, each STATE is normally divided into PROLOGUE, LOOP and EPILOGUE sections. Entry into a given STATE (PROLOGUE) normally causes a group of operations to be performed, these consisting of operations that are performed once only at the entry into the STATE. For complex operations, a CALL is made to an applications subroutine therefor. Relatively simpler operations (i.e. turning devices on or off, clearing memory, presetting memory, etc.) are done directly.

Once the STATE PROLOGUE is completed, the main body (LOOP) is entered. The program (STCK) remains in this LOOP until a change of STATE request is received and honored. On a change of STATE request, the STATE EPILOGUE is entered wherein a group of operations are performed, following which the STATE moves into the PROLOGUE of the next STATE to be entered.

Referring to Fig. 21, on actuation of the machine POWER-ON button 804, the software initialize STATE (INIT) is entered.

In this STATE, the controller is initialized and a software-controlled self-test subroutine is entered. If the self-test of the controller is successfully passed, the system not ready state (NRDY) is entered. If not, a fault condition is signaled.

In the system not ready state (NRDY), background subroutines are entered. These include setting of ready flags, control registers, timers, and the like; turning on power supplies, the fuser, etc., initializing the fault handler, checking for paper jams (left over from a previous run), door and cover interlocks, fuser temperatures, etc.

During this period, the WAIT lamp on console 800 is lit and operation of host machine 10 precluded.

When all ready conditions have been checked and found acceptable, the controller moves to the system ready state (RDY). The READY lamp on console 800 is lit and final ready checks made. Host machine 10 is now ready for operation upon completion of input of a copy run program, loading of one or more originals 2 into document handler 16 (if selected by the operator), and actuation of START PRINT button 805. As will appear hereinafter, the next state is PRINT wherein the particular copy run programmed is carried out.

While the machine is completing a copy run, the controller normally enters the run not print state (RUNNPRT) where the controller calculates the number of copies delivered, resets various flags, stores certain machine event information in the memory, as well as generally conditioning the machine for another copy run, if desired.

The controller then returns to the system not ready state (NRDY) to recheck for ready conditions preparatory for another copy run, with the same state sequence being repeated until the machine is turned off by actuation of POWER OFF button 804 or a malfunction-inspired shutdown is triggered. The last state (TECH REP) is a machine servicing state wherein certain service routines are made available to the machine/repair personnel, i.e. technical representatives.

Referring particularly to Fig. 19, the machine operator uses control console 800 to program the machine for the copy run desired. Programming may be done during either the system not ready (NRDY) or system ready (RDY) states, although the machine will not operate during the system not ready state should START PRINT button 805 be pushed. The copy run includes selecting (using keyboard 808) the number of copies to be made, and such other ancillary program features as may be desired, i.e. use of auxiliary paper tray 102, (push button 810), image size selection (push buttons 818, 819, 820), document handler/sorter selection (push buttons 822, 823, 825, 826), copy density (push buttons 814, 815), duplex or two-sided copy button 811, etc. On completion of the copy run program, START PRINT button 805 is actuated to start the copy run programmed (presuming the READY lamp is on and an original or originals 2 have been placed in tray 233 of document handler 16, if the document handler has been selected).

With programming of the copy run instructions, controller 18 enters a digit input routine, in which the program information is transferred to RAM section 546. The copy run program data pass via main panel interface module 526 to input matrix module 524 and from there is addressed through matrix input select 604, multiplexer 624, and buffers 620 of I/O module 502 to RAM section 546 of CPU module 500.

On entering PRINT STATE, a run event table(Fig. 22) comprised of foreground tasks is built for operating, in cooperation with the background tasks, the various components of host machine 10 in an integrated manner to produce the copies programmed. The run event table is formed by controller 18 through merger of a fixed pitch event table (stored in ROM 545 and non volatile Memory 610) and a variable pitch event table in a fashion appropriate to the parameters of the job selected.

The fixed pitch event table is comprised of machine events whose operational timing is fixed during each pitch cycle such as the timing of bias to transfer roll 75, (TRN 2 CURR), actuating toner concentration sensor 65 (ADC ACT), loading roll 161 of fuser 150 (FUS*LOAD), and so forth, irrespective of the particular copy run programmed. The variable pitch table is comprised of machine events whose operational timing varies with the individual copy run programmed, i.e. timing of pitch fadeout lamp 44 (FO*ONBSE) and timing of flash illumination lamps 37 (FLSH BSE).

The variable pitch table is built by the pitch table builder-from the copy run information programmed in by controller 18 (using the machine control program stored in ROM section 545 and non-volatile memory 610), coupled with event address information from ROM section 545, sorted by absolute clock count and stored in RAM section 546.

The fixed pitch event table and variable pitch table are merged with the relative clock count differences between pitch events calculated to form a run event table shown in Fig. 22.

Referring particularly to Fig. 22, the run event table consists of successive groups of individual events 851. Each event 851 is comprised of four data blocks, data block 852 containing the number of clock pulses (from machine clock 202) to the next scheduled pitch event (REL DIFF), data block 853 containing the shift register position associated with the event (REL SR), and data blocks 854, 855 (EVENT LO) (EVENT HI) containing the address of the event subroutine. The data in the run event table are utilized to control the machine components in a properly-timed sequence initiated by signals from the pitch reset clock 135, machine clock 202, and real time clock 670.

Referring particularly to the timing chart shown in Figure 24, an exemplary copy run wherein three copies of each of two simplex or one-sided originals in duplex mode is made. Referring to Fig. 19, the appropriate button of copy selector 808 is set for the number of copies desired, i.e. three, and document handler button 822, sorter select button 825 and two-sided (duplex) button 811 depressed. The orginals, in this case two simplex or one-sided originals, are loaded into tray 233 of document handler 16 (Fig.

4) and the print button 805 depressed. On depression of button 805, the host machine 10 enters the PRINT state and the run event table for the exemplary copy run programmed is built by controller 18 and stored in RAM section 546. As described, the run event table together with background routines serve, via the multipleinterrupt system and output refresh (through DMA) to operate the various components of host machine 10 in integrated timed relationship to produce the copies programmed.

During the run, the first original is advanced onto platen 35 by document handler 16 where, as seen in Figure 24, three exposures (IST FLASH SIDE 1) are made producing three latent electrostatic images on belt 20 in succession. As described earlier, the images are developed at developing station 28 and transferred to individual copy sheets fed forward (1ST FEED SIDE 1) from main paper tray 100.

The sheets bearing the images are carried from the transfer roll/belt nip by vacuum transport 155 to fuser 150 where the images are fixed. Following fusing, the copy sheets are routed by deflector 184 (referred to as an inverter gate in the tables) to return transport 182 and carried to auxiliary tray 102. The image-bearing sheets entering tray 102 are aligned by edge pattern 187 in preparation for refeeding thereof.

Following delivery of the last copy sheet to auxiliary tray 102, the document handler 16 is activated to remove the first original from platen 35 and bring the second original into registered position on platen 35. The second original is exposed three times (FLASH SIDE 2), the resulting images being developed on belt 20 at developing station 28 and transferred to the opposite or second side of the previously-processed copy sheets which are now advanced (FEED SIDE 2) in timed relationship from auxiliary tray 102. Following transfer, the side two images are fused by fuser 150 and routed, by gate 184 toward stop 190, the latter being raised for this purpose.

Abutment of the leading edge of the copy sheet with stop 190 causes the sheet trailing edge to be guided into discharge chute 186, effectively inverting the sheet, now bearing images on both sides. The inverted sheet is fed onto transport 181 and into an output receptacle such as sorter 14 where, in this example, the sheets are placed in successive ones of the first three trays 212 of either the upper of lower arrays 210, 211 respectively, depending on the disposition of deflector 220.

Other copy run programs, both simple and duplex, with and without sorter 14 and document handler 16, may be envisioned.

In the reproduction system 10, certain self-test routines are provided to check operation of the system controls, memories,and data and address lines. These include static self tests comprising memory check sun test (Figure 25); RAM memory test (Figures 26, 27, 28); non-volatile memory (NVM) test (Figure 29); address wrap-around test (Figure 30); controller interface refresh test (Figure 31); and data transmission to digit display test (Figure 32).

A data transmission to remote modules verifying test (Figure 33), is effected before machine startup and called periodically during machine operation. The self-tests identify for the machine operator the source of the failure through display lamps, which preferably comprise lightemitting diodes (or LED's) 860, 861, 862, 863 on operator console 800 (Figure 19).

LED's 860, 861, 862, 863 correspond to LED 1, LED 2, LED 3 and LED 4 found in the aforementioned self-test tables.

In the memory check sum test (Figure 25), the contents of ROM memory section 545 (Figure 6) are added and that sum is compared with a check sum count (CHECK SUM). If the numbers agree, a check is made to determine if the memory section is active, If not, the memory is bad. If the memory section is active, the normal program is continued. If the sums do not agrees, a check is made to determine if the memory is active. If the memcy is off, i.e.

not active, the CPU memory printed wiring board (PWB) is bad. The controller failed (CPU FAIL) routine is called and the system shutdown. If the memory is active, the memory is disabled and the test repeated.

The check sum count (CHECK SUM) is obtained from the first run through of memory check sum comparison routine.

The check sum count so obtained is stored in memory for subsequent use in this routine.

The memory check sum test routine includes instructions for resetting the watch dog timer 614 each time around the test loop (RESET WATCH DOG TIMER). This is required because the total test time is greater than the time-out setting of the watch dog timer. Thus, if not reset on each loop through the test, the timer 614 will time out, with consequent setting of the fault flip flop and shutdown of the system.

In the RAM memory test (Figures 26, 27, 28) a check is run through the scratch pad and flag portions of RAM memory sections 546 to see if any output drivers routine (Figure 31) for CPU interface module 504 part I loops a test bit through each of the data lines (total 256) to the remotes Do--D7 (Fig. 12) and checks to see if the readback is the same as the output. A second portion checks the address lines (total 32) in the same manner. The routine also determines the identity of the printed wiring board (PWB) at fault from the test results of the address wrap-around test or the controller interface refresh test. The appropriate subroutine IOP FAIL or CTL INTOF is called to turn on the appropriate indicator LED's 860, 861 or LED 863 on console 800.

In the data transmission to digit display test routine (Figure 32), data transmission to the main panel interface module 546, through which the digit display of control console 800 (Figure 32) is effected, is checked by looping a test bit through the data lines Do--D7 (total 256) and reading back data sent. The data read back are compared with the data sent and any failed bits are saved for use in identifying the fault.

In the data transmission to remote modules verifying test routine (Figure 33), a static check is made before system startup of the input matrix module 524 to determine if data are being transmitted between module 524 and the remote modules Do- D7. In this test, a test bit is sent through each data line (total 256) and read back. A comparison is made between the bits sent, and any failed bits are saved. The failed bits saved from the data transmission to digit display test and the static data transmission to remote modules verifying test are used in the second portion of the routine to identify either the input matrix module printed wiring board (PWB) or the main panel interface module PWB as the problem, and turn on the appropriate LED combination 861, 862 or 860, 861, 862.

A running check of data transmission is made periodically during machine operation. In this check, a test bit is sent to each remote module Do-D7, and a comparison is made between the bit sent and the bit returned. If the comparison shows the bit sent differs from the bit returned, the failed bit is checked to see if the same bit failed earlier. Should the same bit fail twice in a row, a jump is made to the selftest start routine (SEC STRT). This routine disables the interrupts, allowing the watchdog timer 614, (Figure 10) to time out and shutdown the machine. The static selftest routines, which must be redone before restart of the machine 10 is allowed, locate the fault and identify the fault to the operator through the use of LED's 860, 861, 862, 863.

Miscellaneous routines comprise subroutines called during various ones of the self-test routines. These include a delay routine (V DELAY); I/O safeline pulse routine (SAF PULS); and failure stop routines (CPU, FAIL: MNPL IOF; IOP FAIL; MNPL CK; MTX FAIL; and CTL INTF).

Referring to the controller operating cycle block diagram of Figure 21, the aforedescribed static self-test routines are initially performed after power to controller 18 is established (D.C. POWER on).

Following completion of the static portion of the data transmission to remote modules verifying test, the self-test routine sequence is exited and the controller enters the software initialization (INIT) state of the background or state checker routine (STCK).

During machine operations, controller 18 is in one of the initialization, system not ready, system ready, print, system running not print, and service states until shutdown.

When the controller is in the system not ready, system ready, print, and system running not print states, the running portion of the data transmission to remote modules verifying test (TST LP 4) is periodically called to verify transmission of operating data to the remotes. Where a problem is discovered, the machine is shutdown and return is made to the static self-test routines, i.e. memory check sum comparison (SEC STRT) to determine where the fault lays as described.

WHAT WE CLAIM IS: 1. A method of verifying transmission of control signals to a controlled element in an electrographic machine including the steps of: a. applying a test signal to said controlled element; b. reading back the signal output from said controlled element; c. comparing the signal output of said controlled element with the applied test signal; and d. declaring a machine fault when the signal output differs significantly from the test signal.

2. The method according to claim 1, in which the steps are taken periodically during operation of said machine.

3. The method according to claims 1 or 2, in which the step of declaring a machine fault is taken only when the signal output from a controlled element differs from the test signal at least twice in succession.

4. A method according to any of the preceding claims, including the steps of: a. addressing a first test signal command to each of a first group of controlled elements; b. addressing a second test signal

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (14)

**WARNING** start of CLMS field may overlap end of DESC **. routine (Figure 31) for CPU interface module 504 part I loops a test bit through each of the data lines (total 256) to the remotes Do--D7 (Fig. 12) and checks to see if the readback is the same as the output. A second portion checks the address lines (total 32) in the same manner. The routine also determines the identity of the printed wiring board (PWB) at fault from the test results of the address wrap-around test or the controller interface refresh test. The appropriate subroutine IOP FAIL or CTL INTOF is called to turn on the appropriate indicator LED's 860, 861 or LED 863 on console 800. In the data transmission to digit display test routine (Figure 32), data transmission to the main panel interface module 546, through which the digit display of control console 800 (Figure 32) is effected, is checked by looping a test bit through the data lines Do--D7 (total 256) and reading back data sent. The data read back are compared with the data sent and any failed bits are saved for use in identifying the fault. In the data transmission to remote modules verifying test routine (Figure 33), a static check is made before system startup of the input matrix module 524 to determine if data are being transmitted between module 524 and the remote modules Do- D7. In this test, a test bit is sent through each data line (total 256) and read back. A comparison is made between the bits sent, and any failed bits are saved. The failed bits saved from the data transmission to digit display test and the static data transmission to remote modules verifying test are used in the second portion of the routine to identify either the input matrix module printed wiring board (PWB) or the main panel interface module PWB as the problem, and turn on the appropriate LED combination 861, 862 or 860, 861, 862. A running check of data transmission is made periodically during machine operation. In this check, a test bit is sent to each remote module Do-D7, and a comparison is made between the bit sent and the bit returned. If the comparison shows the bit sent differs from the bit returned, the failed bit is checked to see if the same bit failed earlier. Should the same bit fail twice in a row, a jump is made to the selftest start routine (SEC STRT). This routine disables the interrupts, allowing the watchdog timer 614, (Figure 10) to time out and shutdown the machine. The static selftest routines, which must be redone before restart of the machine 10 is allowed, locate the fault and identify the fault to the operator through the use of LED's 860, 861, 862, 863. Miscellaneous routines comprise subroutines called during various ones of the self-test routines. These include a delay routine (V DELAY); I/O safeline pulse routine (SAF PULS); and failure stop routines (CPU, FAIL: MNPL IOF; IOP FAIL; MNPL CK; MTX FAIL; and CTL INTF). Referring to the controller operating cycle block diagram of Figure 21, the aforedescribed static self-test routines are initially performed after power to controller 18 is established (D.C. POWER on). Following completion of the static portion of the data transmission to remote modules verifying test, the self-test routine sequence is exited and the controller enters the software initialization (INIT) state of the background or state checker routine (STCK). During machine operations, controller 18 is in one of the initialization, system not ready, system ready, print, system running not print, and service states until shutdown. When the controller is in the system not ready, system ready, print, and system running not print states, the running portion of the data transmission to remote modules verifying test (TST LP 4) is periodically called to verify transmission of operating data to the remotes. Where a problem is discovered, the machine is shutdown and return is made to the static self-test routines, i.e. memory check sum comparison (SEC STRT) to determine where the fault lays as described. WHAT WE CLAIM IS:

1. A method of verifying transmission of control signals to a controlled element in an electrographic machine including the steps of: a. applying a test signal to said controlled element; b. reading back the signal output from said controlled element; c. comparing the signal output of said controlled element with the applied test signal; and d. declaring a machine fault when the signal output differs significantly from the test signal.

2. The method according to claim 1, in which the steps are taken periodically during operation of said machine.

3. The method according to claims 1 or 2, in which the step of declaring a machine fault is taken only when the signal output from a controlled element differs from the test signal at least twice in succession.

4. A method according to any of the preceding claims, including the steps of: a. addressing a first test signal command to each of a first group of controlled elements; b. addressing a second test signal

command to each of a second group of controlled elements; c. comparing the actual signal output of each element with the signal output commanded by the respective test signal; and d. declaring a machine fault when the actual signal output of any element differs significantly from the signal output commanded.

5. The method according to claim 4 including the further step of readdressing said first and second test signal commands to the respective controlled elements.

6. The method according to claim 4 or 5, when performed prior to a copying operation of said machine.

7. The method according to any of the preceding claims, in which the test signal is directed through the lines utilized by a machine controller to address the copyprocessing elements of the machine.

8. The method of claim 7, including the step of testing the address lines in response to a detection of a fault to determine if the fault was introduced by the address lines are at fault.

9. The method according to any of the preceding claims, in which the test signal is directed through each of the interface lines between said machine and a machine controller, and in which startup of said machine is prevented when a fault is declared.

10. The method according to any of the preceding claims, including the steps of: a. summing the contents of the memory of a machine controller; and b. comparing the measured sum with a predetermined check sum; and c. preventing operation of said machine when the sums differ from each other.

11. The method according to Claim 10, including the step of retaining a measured sum for use as a check sum in a later verification process.

12. Means which verifies transmission of control data to the operating components of an electrographic apparatus, the verification means including: means which periodically send test data to said components; means which compares the test data sent to said components with the data returned from said components; and means which shut down said apparatus when the test data returned from said components differ from the test data sent to them.

13. The data transmission verification means of claim 12 including: means for temporarily retaining the identity of any operating component having different test and return data pending the next data verification check; and means for identifying any operating component from the next succeeding data verification check that gives rise to different test and return data; the shut-down means being operated when an identity comparison reveals that the same component was faulty on both occasions.

14. The method substantiafly as herein described with reference to, and as illustrated in, the accompanying drawings.