WO1993002411A1

WO1993002411A1 - Controller for plural printers

Info

Publication number: WO1993002411A1
Application number: PCT/US1992/005863
Authority: WO
Inventors: Gerald Jay Denny; Robert A. Garrow
Original assignee: Athenix Corp
Current assignee: Athenix Corp
Priority date: 1991-07-19
Filing date: 1992-07-17
Publication date: 1993-02-04
Anticipated expiration: 1994-01-19

Abstract

A structure and a method provide a controller module sharable amongst a number of laser printers. The controller module of the present invention comprises an interface to the host processor, processor means for performing graphics data processing and image rendering functions, and a plurality of point-to-point interfaces with a number of external printers with simplified constructions. In one embodiment of the present invention, the controller is integrated with a host computer and communicates with the host computer over a local bus of the host computer. In another embodiment, the controller is a stand-alone device capable of communicating with one or more host computers in a computer network. The printer in accordance with the present invention can coexist in a computer with conventional printers each having a dedicated controller.

Description

- 1 - CONTROLLERFORPLURALPRINTERS

5 FIELD OF THE INVENTION

This invention relates to computer system design, and in particular, relates to the design of peripheral equipment (e.g. laser printers) to be used in a computer network environment.

10 DESCRIPTION OF THE RELATED ART

A conventional laser printer is typically equipped with a controller which provides all controlling functions, such as graphics data processing, the printing functions and the data communication functions, necessary

15 to exist as a stand-alone peripheral device in the computer network. Such controller is not shared amongst other laser printers which may exist on the computer network.

Figure 1 is a block diagram of a conventional laser

20 printer 100. As shown in Figure l, laser printer 100 has a serial interface 101 and a parallel interface 102 for communication with a host computer over a dedicated connection or over a computer network. Laser printer 100 has a controller module 103, which comprises (i) a central

25 processor unit (CPU) for providing the controlling functions of the laser printer, such as controlling the paper-handling mechanism 104, graphics data processing for handling graphics data and rendering the image to be printed, and providing data communication functions over

30 the serial and parallel interfaces 101 and 102; (ii) a graphics processing unit (GPU) , if provided, for handling graphics data and rendering the image to be printed; (iii) a random access memory (RAM) for use by both the CPU and the GPU ; and (iv) a read-only memory unit (ROM) for storing software used by the CPU and the GPU. In addition, at the user's option, the controller of many laser printers allows capability and performance expansion by accepting additional ROMs, RAMs and additional network communication interfaces. In many printers, special fonts and symbols are often provided as plug-in cartridges the user can optionally purchase.

Controller module 103 controls the operations of an user interface 105, which typically interacts with the human user over a set of switches and display messages. The settings of the user interface 105 sets up the parameters for the circuits in block 106 which drive the printing hardware, i.e. paper-handling mechanism 104, the laser printing mechanism and toner module 107. Circuits in block 106 communicate with the CPU in controller module 103 and effectuate printing by controlling the operations of the printing hardware.

In an office environment, for example, multiple laser printers may exist on the same network to be shared by the users of the office. In each network may be one or more host computers. Each laser printer is given a network address and thus can be addressed by any of the host computers on the network, or dedicated to a designated host computer if desired. Thus, to provide maximum efficiency, the laser printers on the network can be shared by users, who may be physically located at different workstations. Figure 2 shows such a network 200 having two laser printers 201a and 201b, controlled by dedicated controllers 204a and 204b respectively, communicating over a local area network 202 (e.g.

Ethernet, Appletalk, or Novell) with a host computer 203.

Because the graphics data processing necessary for laser printers is computationally intensive, affordable computational hardware is often slower than the printer hardware (e.g., it takes longer to render an image than to print it) . However, higher performance computational hardware drives up the cost of the laser printer. Therefore, if this higher cost can be shared by a number of printers, faster printing operations can be achieved at reasonable cost per printer. Also because each conventional laser printer is designed to be stand-alone peripheral device provided with full capability to communicate with the host processors of the computer network, the cost of a conventional laser printer is necessarily higher than if such capability is provided by a resource which can be shared. In addition, in a typical office environment, it is seldom that a large number of laser printers are all printing at the same time. Hence, significant improvement in efficiency can be achieved in such environment if a controller can be shared by a number of laser printers.

SUMMARY OF THE INVENTION

In accordance with the present invention, a structure and a method provide a controller module sharable amongst a number of laser printers having simpler construction than the laser printers of the prior art. The controller module of the present invention comprises an interface to the host processor, processor means for performing graphics data processing, image rendering and remote printer control functions, and a plurality of point-to-point interfaces for communicating with a number of external printers having simplified constructions. Each printer in accordance with the present invention is provided only with a scan-line buffer for a fraction of a line to a few lines of a rendered image, a point-to-point interface to communicate with the external controller, and a microcontroller to control the printing hardware. In one embodiment of the present invention, the controller is integrated with a host computer and communicates with the host computer over a local bus of the host computer. In another embodiment, the controller is a stand-alone device capable of communicating with one or more host computers in a computer network. The printer in accordance with the present invention can coexist in a computer network with conventional printers each having a dedicated controller.

Because the controller in accordance with the present invention is shared by a number of printers, the construction of each printer is significantly simplified. Since the cost of the controller is shared by a number of such simplified printers, the cost for providing multiple printers on a network environment is significantly reduced. By matching the performance of the shared controller to the combined capability and pattern of usage of the printers, such benefits described above can be provided without significant performance degradation. The present invention is better understood upon consideration of the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a block diagram of a conventional laser printer 100 showing a controller module 103 controlling printing hardware blocks 104-107.

Figure 2 shows two conventional laser printers 201a and 201b communicating over a local area network 202 with a host computer 203.

Figure 3 is a block diagram of a computer network 300 including a stand-alone controller module 301 for controlling multiple simplified laser printers in accordance with the present invention.

Figure 4 is a block diagram of a computer network 400 including a controller module 401, which is integrated with host computer 402, for controlling multiple simplified laser printers in accordance with the present invention.

Figure 5 is a block diagram of a simplified laser printer 500 in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a sharable controller for a number of laser printers of simplified construction. The sharable controller may coexist in the same computer network with other laser printers in the prior art having non-sharable controllers.

Figure 3 is a block diagram of a computer network 300 including a stand-alone controller module 301 for controlling multiple simplified laser printers in accordance with the present invention. In Figure 3, a host computer 302 and a stand-alone controller module 301 are both devices on a computer network 300. Computer network 300 can be any suitable computer network, such as Ethernet, AppleTalk or Novell. Controller 301 is connected to a number of "simplified" laser printers (to be discussed below) , such as laser printer 303a and 303b. Controller 301 provides a central processing unit for network functions and remote control of the simplified printers, a graphics processing unit for graphics data processing, a random access memory (RAM) for graphics data and program storage, and a read-only memory (ROM) for storing the software for the graphics data processing functions. In addition, depending on the type of computer network used to implement computer network 300, controller 301 provides a suitable network interface (not shown) . Controller 301 provides the data processing functions of a conventional laser printer, such as rendering images. However, unlike a conventional controller which provides such data processing functions to only one attached laser printer, controller 301 provides such data processing functions to a number of specialized simplified laser printers, such as laser printers 303a and 303b. Because controller 301 provides the interface to the computer network, communication between a simplified laser printer and controller 301 can be accomplished, and is in fact provided, over a dedicated point-to-point connection. Thus, controller 301 has a number of point-to-point communication ports for communicating with a number of simplified laser printers. Like conventional laser printer controllers, controller 301 can also be provided with the ability to accept additional RAM, font cartridges and other add-on devices for incremental performance and capability enhancements. It is envisioned that, in some applications, it is desirable to hold in controller 301*s memory multiple rendered images for printing in multiple laser printers. Holding multiple rendered images in memory allows controller 301 to control multiple laser printers simultaneously without incurring the cost of loading and unloading memory when switching from addressing one laser printer to another. Flexibility in the amount of RAM that can be installed allows optimizing controller 301, with respect to the usage pattern and the complexity of images printed, for the specific computer network in which controller 301 is deployed. It is also envisioned that, since only one central processing unit and one graphics processing unit are required for multiple printers, such processing units may be implemented by very high performance hardware to achieve increased speed of image rendering and at an actual reduced "per printer" cost.

Alternatively, in accordance with the present invention, the shared controller can be integrated on the local bus of a host computer. This embodiment is shown in Figure 4. In Figure 4, controller 401 is integrated with host computer 402 and communicates with host computer 402 over a host bus 403. The EISA (Extended Industry Standard Architecture) bus, for example, is a host bus available on a large number microprocessor-based host computers that can be used as a host bus to which controller 401 can be installed. However, unlike controller 301 of Figure 3, because controller 401 is integrated with host computer 402, controller 401 need not be provided with the ability to communicate with other devices on a computer network. Any communication between controller 401 and devices on a computer network to which host computer 402 is interfaced - 7 - may be handled through host computer 402. By avoiding the cost of providing a direct network interface to the computer network, controller 401 can be provided at an even lower cost than controller 301 of Figure 3. Controller 401 provides the same graphics data processing functions as those provided by controller 301 to each of the attached simplified laser printers, such as simplified laser printers 404a and 404b. Each of the simplified laser printers is connected to controller 401 over a point-to-point connection, the same as that provided by controller 301 of Figure 3. The configuration of Figure 4 is best suited for applications in which the host computer 402 is the exclusive client for controller 401.

Figure 5 is a block diagram of a simplified laser printer, such as any of the simplified laser printers 303a, 303b, 404a and 404b shown in Figures 3 and 4. As shown in Figure 5, a simplified laser printer comprises a simplified controller 501. This simplified controller 501 has a point-to-point connection for communicating with a shared controller, such as controller 301 of Figure 3, or controller 401 of Figure 4. In addition, the simplified controller 501 has a central process unit for providing local controlling functions, such as the controlling functions for the logic interface 505, which in turn operates the human interface 502, the paper-handling mechanism 503, and the laser printing mechanism and toner module 505. Since the graphics data processing functions are provided by the shared controller, such as controller 301 of Figure 3, no data handling capability need to be provided in the simplified controller 501. As a result, only a small buffer, such as a scan-line buffer storing values of the pixels in one line of the image, is necessary. These pixel values are provided to the laser printing mechanism 504 without further processing by controller 501.

Since the cost of providing the graphics data processing unit, the random access memory and the read- - 8 - only memory necessary for graphics data processing form a significant portion of the cost of a conventional laser printer, the simplified laser printer having off-loaded such functions to the sharable controller of the present invention, can be provided at a cost significantly less than that of a conventional laser printer.

Because the memory and high performance processor requirements necessary to provide the network interface and graphics data processing in a laser printer controller are shared in accordance with the present invention among a number of simplified laser printers, the cost of a network having multiple laser printers is also significantly reduced. Further, in a network in which not all laser printers are expected to be activated (i.e. printing) at the same time, the benefit of cost reduction can be achieved with minimal performance degradation, since the shared controller of the present invention may be serving only one simplified laser printer at any given time. Under such condition, the shared controller performs for the activated laser printer like the dedicated conventional laser printer controller. If the graphics processor in the shared controller is of high enough performance (e.g. able to render a complete page of image in a shorter period of time than the print mechanism can print a page of image) and if the shared controller is provided with a large enough random access memory (e.g. large enough to provide several frame buffers for several attached laser printers) to allow the shared controller rapid multiplexing between rendered images of several simplified laser printers, performance degradation can be made insignificant.

The above detailed description is provided to illustrate the specific embodiments of the present invention, and is not intended to be limiting. Numerous variations and modifications are possible within the present invention. The present invention is defined by the following claims.

Claims

1. A controller for multiple printers, comprising: interface for communicating with a host computer; a plurality of point-to-point communication interfaces each for communicating with a printer; and means for graphics data processing and image rendering.

2. A controller as in Claim 1, wherein said controller is housed in the same cabinet as said host computer, communicating with said host computer over a local bus of said host computer.

3. A controller as in Claim 1, wherein said controller acts as a stand-alone device on a computer network, and communicates with said host computer over said computer network.

4. A laser printer, comprising: a point-to-point interface to a sharable controller; a scan-line buffer for receiving from said sharable controller rendered graphics data for printing an image; and microcontroller means for controlling the printing hardware.

5. A method for providing a controller for multiple printers, comprising the steps of: providing said controller an interface for communicating with a host computer; providing said controller a plurality of point-to-point communication interfaces each for communicating with a printer; and providing said controller means for graphics data processing and image rendering.

6. A method as in Claim 5, wherein said method further comprises the step of providing said controller in the same cabinet as said host computer, such that said controller communicates with said host computer over a local bus of said host computer.

7. A method as in Claim 5, wherein said method further comprises: the step of providing said controller as a stand-alone device on a computer network, such that said controller communicates with said host computer over said computer network.

8. A method for providing a laser printer, comprising the steps of: providing a point-to-point interface to a sharable controller; providing a scan-line buffer for receiving from said sharable controller rendered graphics data for printing an image; and providing microcontroller means for controlling the printing hardware.