WO1988003289A1

WO1988003289A1 - Interchangeable personality modules for a computer terminal

Info

Publication number: WO1988003289A1
Application number: PCT/US1987/002794
Authority: WO
Inventors: Gerard A. Desilets, Jr.
Original assignee: Visual Technology, Incorporated
Priority date: 1986-10-23
Filing date: 1987-10-23
Publication date: 1988-05-05
Also published as: KR880005505A; IL84130A0; AU8235687A

Abstract

A versatile computer terminal (10) having those memory circuits (26) which include instructions which, when executed by the terminal's microprocessor (32), define the personality of the terminal arranged on a separate printed circuit board (24) that can be easily replaced through an access door (18) located on the base of the computer terminal (14).

Description

Interchangeable Personality Modules for a Computer Terminal

The present application is related to co-pending application Serial No. 922,669, filed October 24, 1986 by Edward Knapton and Ernest Vincent, the specification of which is incorporated herein.

BACKGROUND OF THE INVENTION The present invention relates to a versatile computer terminal, and to a method of using the same. More particularly, it relates to a CRT terminal that can easily be modified to be compatible with different computer systems.

Modern display terminals are packaged and sold as sophisticated equipment that is far more complex than a simple cathode ray tube (CRT) display unit. These terminals are frequently sold together with a keyboard, a data link for receiving data from a computer, and microprocessors for carrying out the functions of driving the CRT, monitoring the keyboard, and controlling communications through the data link. The microprocessors also control certain features such as scrolling and cursor controls and other controls that facilitate use of the terminal. These microprocessors also allow the terminal to perform limited data processing or word processing functions, and include special modules containing read-only memories.

The inclusion of the above features (and many features not discussed) has improved the usefulness of the terminals, but does have certain disadvantages. A primary disadvantage is that the microprocessors require that each terminal be specifically designed for use with a limited number of computer systems. For example, a computer terminal that can be operated with a Burroughs computer may not be usable with a Wang computer. The ability of a computer terminal to be used with a computer system is generally referred to as the compatibility (or personality) of the terminal. If a computer terminal has the same compatibility features as a different terminal, that terminal is described as emulating the different terminal.

Prior to the present invention, computer terminals were generally mounted on a base which contained circuitry necessary to interface the terminal with the host computer or system. This circuitry was generally mounted on a large printed circuit board encased within the base.

If for some reason, the compatibility of the terminal had to be changed, the base was dismantled and the printed circuit was removed so that the necessary modules could be replaced. Such a process is relatively difficult and usually was done only by trained technicians. Needless to say, the compatibility or personality of such a terminal was rarely changed.

An attempt at simplifying this problem is found in U.S. Patent No. 4,527,250 issued to Galdun et al. on July 2, 1985. The Galdun et al. patent discloses a computer terminal having an "application module" which is removably connected to the computer terminal. The application module includes a keyboard, an application memory for storing instructions that interpret keyboard inputs, and interface means for coupling the application memory and the keyboard to a controller portion of the terminal. A portion of the personality of the computer terminal can be changed by replacing the application module, although the terminal can continue to function as a CRT monitor even without the application module. Instructions stored in a permanently installed PROM continue to direct the operation of the terminal even without an application module. U.S. Patent No. 4,063,221 issued to

Watson et al. on December 13, 1977, and discloses a programmable calculator that has a keyboard and ROM receptacles. Plug-in ROM modules are inserted in the receptacles and define the functions assigned to the various keys of the calculator. The application of this patent is limited to calculators, and is not particularly relevant to the interfacing of the calculator with a computer system. The prior art devices contain several disadvantages. None of these devices enables a user to change completely the personality of a terminal by the convenient replacement of a small, easy to ship and store element. They require either the replacement of a large unit which is comparatively bulky and expensive, or the disassembly of the computer terminal base. Further, the absence of complete changeability of the attributes of the computer terminal limits the variety of host computers compatible with the terminal.

SUMMARY AND OBJECTS OF THE INVENTION In view of the foregoing limitations and shortcomings of the prior art, as well as other disadvantages not specifically mentioned above, it should be apparent that, prior to the present invention, there existed a need in the art for a convenient and aesthetic means for modifying computer terminals to alter their compatibility. It is, therefore, a primary object of this invention to fulfill that need by providing a computer terminal having its case and electronic components designed for easy replacement of certain of the components.

More particularly, it is an object of the present invention to provide a computer terminal wherein access may be easily had to the internal components thereof. A further object of the present invention is to locate certain of the electronic components of a computer terminal in such a manner so as to facilitate their replacement.

It is another object of the present invention to locate in a specific area only the electronic components of a computer terminal that must be replaced in order to alter the personality of the terminal. Another object of the present invention is to provide a computer terminal wherein the electronic components of the terminal that must be replaced in order to alter the personality of the computer are located on a separate printed circuit board to facilitate their replacement.

It is yet another object of the present invention to provide a computer terminal having a personality which the end user is able to change easily. It is yet another object of the present invention to provide a computer terminal that has the personality-altering components arranged on a single unit that can be easily removed and shipped to an end user.

Briefly described, the aforementioned objects are accomplished according to the invention by arranging the electronic components necessary for defining the personality of the terminal on a small printed circuit board that is separate from the main printed circuit board on which the remaining terminal components are arranged. The small circuit board is equipped with electrical connectors and is designed to be removably plugged into like connectors on the main circuit board. A special access door is incorporated into the terminal base so as to provide a convenient manner in which to access the small circuit board. With the foregoing and other objects, advantages, and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several views illustrated in the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view of a computer terminal in accordance with the present invention; Figure 2 is a top plan view of the base of the computer terminal in accordance with the present invention; Figure 3 is a top plan view of the replacement circuit board of the present invention;

Figure 4 is a block diagram of the circuits used in the computer terminal; and

Figures 5A and 5B are schematic diagrams of the circuits used in the personality module. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now in detail to the drawings, wherein like parts are designated by like reference numerals throughout, there is illustrated in Figure 1 a computer terminal according to the present invention designated by reference numeral 10. The terminal 10 includes a cathode ray tube (CRT) display monitor 12 mounted on a base 14. A connecting stem 16 provides a connection between the monitor 12 and the base 14, while allowing the monitor to pivot with respect to the base in a known manner.

The base 14 is provided with an access door 18 that can be slid horizontally away from the base in the direction of arrow A, as illustrated in Figure 2. The access door 18 is shown in Figure 2 removed.from the base, exposing the recess 20, in which the door fits.

The door is similar to those frequently used to cover battery compartments in portable radios. Preferably the door 18, like the base 14, is made from rigid plastic. The base has tracks 19 on which the door 18 slides, and the door 18 may have releasable locking means, such as tabs 17 which engage in recesses (not shown) in the base 14. With reference to Figures 2 and 3, mounted in the terminal is a personality module 22 which includes a small printed circuit board 24. Mounted on the board 24 are Electronically Programmable Read Only Memories (EPROMs) , as well as other integrated circuits as required. Other types of Read Only Memories (ROMs) or Random Access Memories (RAMs) may be installed on the circuit board 24 as appropriate for the desired personality. These circuits are designated generally by reference numeral 26, and they are incorporated into modules having different personalities, each module being designed to allow the computer terminal in which it is used to emulate computer terminals such as the DEC VT220, WYSE 50 plus, Lear siegler, and Hazeltine 1500, among others. Connectors 28 are mounted on the printed circuit board 24 for providing address and data busses, control signals and power to the circuits 26. Jumper terminal pairs 30 are also provided to allow rapid and efficient modification of the personality module, as will be described in greater detail below in connection with Figure 5. The personality module 22 is a component of the complete circuitry necessary for the computer terminal 10. Figure 4 shows a block diagram of the circuitry of a terminal according to the present invention. It will be understood by those skilled in the art that any suitable microprocessor, including the MC68000 manufactured by Motorola, may be used in the context of the present invention with appropriate changes to the circuitry. The main circuit board of the terminal, that is everything outside the personality module 22, includes a central processing unit (CPU) 32 which controls the operation of the terminal by executing instructions stored in memory circuits, such as EPROMs, located in the personality module 22. As already known in the digital processing art, these instructions are communicated to the CPU 32 along a data bus 34 from memory locations selected by the CPU through an address bus 36. The control signals and power required by the circuits in module 22 are indicated generally by conductor 35.

The CPU 32 directs the operation of the other components of the terminal so as to form the desired alphanumeric characters or other information on the CRT display 42. These other components may include a separate CRT controller circuit 40 and additional memory circuits 44 and 46 which may be arranged to provide a bitmapped output display 42, as described in the aforementioned copending application.

In a computer terminal according to the present embodiment, a 1056 x 800 bit map for the monitor 42 is effectively created in the memory circuit 44 which may advantageously be comprised of dynamic random access memory (DRAM) ICs. In a bit-mapped terminal the pixels on the display monitor are in one-to-one correspondence with the bit locations in a memory. Data is written into the bit-map by the CPU 32 and is then read from the bit-map and written onto the CRT display 42 by the CRT controller 40. To avoid contention for the data bus 34 between the CPU 32 and controller 40, tri-state latches 48 selectively isolate the CPU from the controller thereby allowing the CPU to communicate with the personality module 22 while the controller communicates with the bit-map memory 44. The address lines 54 of the memory 44 are shared by the CPU 32 and controller 40 through the well-known operation of a multiplexer 52.

The CPU 32 and controller 40 may also communicate with an attribute memory 46 which, in one embodiment, may be CMOS static RAM ICs 46. To enhance the writing speed of the terminal 10, attributes of the characters to be written onto the display 42 are stored in an attribute memory 46. These attributes include the grouping of bits in the bit map which compose the alphanumeric character positions on the display, as well as blinking, reverse-video and highlighting of the characters. The contents of the attribute memory 46 are accessed in the usual manner through a SRAM data bus 60 and a SRAM address bus 62 by either the CPU 32 or the CRT controller 40. The CPU 32 can both read and write data to the attribute memory 46, while controller 40 only reads data from the memory 46. During each horizontal blanking interval of the CRT 42, the controller 40 reads one line of character attributes from the memory 46.

According to the present embodiment the data comprising the bit-map is read from the memory 44 in a sequence of 16-bit parallel words which are converted to a serial bit stream by a shift register 56. The output of the shift register 56 is combined with the output of the attribute memory 46 by a mixer 58. In this way the desired attributes of characters on the display 42 are imposed on the contents of the bit¬ map memory, thereby providing the versatility of a bit-mapped terminal for alphanumeric applications without requiring unreasonable memory capacity and speed.

Also shown in Figure 4 are communication interfaces 38 which control the input and output of digital data from the terminal 10. The interfaces 38 may include several universal synchronous receiver transmitters (UARTs) for providing several serial-data I/O ports to the terminal. It is common to have at least three of these ports, one each for a keyboard, a printer and the host computer. Parallel-data I/O ports may also be provided to the terminal 10.

The personality of the terminal 10 is determined by the instructions stored in the memory circuits of module 22 as they are executed by the CPU 32. The particular printing font as well as the size of the characters printed on the CRT 42 are determined in a well-known manner by the stored instructions. The creation of underlining and blanks as well as the cursor displayed on the CRT 42 is also determined by the CPU's execution of the stored instructions. Scrolling of the displayed information, whether smooth or jump-wise, and various set-up parameters of the terminal, such as 80-column or 132-column modes, tabs and key functions are also part of the terminal's personality and thus determinable by the module 22.

Figure 5 shows a schematic diagram of the circuitry mounted on PC board 24 in one embodiment of the present invention. The module circuit shown in Figures includes four EPROM ICs, designated 26, which are connected to the data bus 34 and address bus 36. Depending on the particular memory circuits and CPU employed, the number and arrangement of the address lines and data lines may vary. A terminal according to the present invention which employs a MC 68000 CPU can advantageously use a 16-bit wide address bus and a 16-bit wide data bus divided into an upper and lower half. The bus signals, control signals and power are connected to the circuits on the board 24 through two connectors 28 also mounted on the board. These connectors mate with other similar connectors on the main circuit board of the terminal 10, providing for easy interchangeability of the module 22.

Control signals such as PROM-S and AS which aid in controlling the operation of the memory circuits 26 are brought to the board 24 through the connectors 28. The PROM-select signal, PROM-S, enables the EPROMs 26. In the present embodiment, this signal goes to logic low, enabling the EPROMs, only when certain addresses are present on the address bus 36. Those certain addresses correspond to the memory locations of the memory circuits in the personality module 22 only. The address-strobe signal, AS, is logic low when the voltage levels on the address bus 36 are valid. The address-strobe signal is a standard control signal generated by the MC 68000 microprocessor. One or more additional ICs such as NAND gates 27 may also be provided in the module 22 to derive additional memory control signals as required. As appropriate to the desired personality for the terminal 10, other signals and voltages may also be routed through connectors 28 and modified by additional components on the personality board 24 for use by the main circuit board.

Since EPROMs and other memory circuits are manufactured with a range of storage capacities, including for example 64K, 128K, 256K and 512K, a common PC board design can be used in the modules 22 by including a number of jumper contact pairs 30. Depending on the particular subset of pairs connected, the control signals necessary for operating the different-size memory circuits 26 can be derived. Table I shows various memory capacities which can be provided by the personality module 22 using particular standard memory IC types for the circuits 26 (U1-U4) , and jumper conditions (W1-W14) . NAND gates 27 are provided by another standard IC (U5) .

In the terminal of the present embodiment, memories having access times less than 250 nanoseσ are used to avoid slowing the operation of the MC 68000 CPU. However, it will be understood that any suitable type of memory can be used in the module 22 by appropriate modification of the instructions stored in the memory for execution by the CPU.

Also shown in Figure 5 is an array of capacitors 29 which provide filtering and noise rejection for the power supplied to the board 24.

Besides accommodating different standard memory ICs to provide the storage capacity required by the instructions necessary to

TABLE; MODULE CONFIGURATIONS

Firmware

Size Ul U2 U3 U4 U5

16K 2764 2764

32K 27128 27128

64K 27256 27256

80K 27256 2764 27256 2764 74LS00

96K 27256 27128 27256 27128 74LS00

128K 27256 27256 27256 27256 74LS00

128K 27512 27512

144K 27512 2764 27512 2764 74LS00

160K 27512 27128 27512 27128 74LS00

196K 27512 27256 27512 27256 74LS00

256K 27512 27512 27512 27512 74LS00

Firmware

Size W2 Wl W10 W6 W5 W3 W4 W14 W13 Wll

16K IN IN IN

32K IN IN IN

64K IN IN IN

8OK IN IN IN IN IN

96K IN IN IN IN IN

128K IN IN IN IN IN

128K IN IN IN

144K IN IN IN IN IN

160K IN IN IN IN IN

196K IN IN IN IN IN

256K IN IN IN IN IN

determine the personality of the terminal 10, the personality module 22 may also include other devices according to the capability desired for the terminal. For example, additional RAM ICs may be provided to allow the terminal itself to perform data processing functions independent of the host computer. These functions might include controlling additional I/O ports, modems, etc. as well as providing nonvolatile special function keys on the keyboard attached to the terminal.

The ease with which a personality module may be replaced by untrained end users allows significant flexibility to accommodate revisions and improvements of the instructions stored in the memory circuits of the module. Specific requirements of individual end users may also be addressed by providing user specific personality modules.

Without the personality module 22, the terminal 10 cannot function as a terminal. Since the personality module 22 contains all the circuitry that makes the terminal compatible with a system, all the basic terminals can be manufactured alike. This is an advantage in that it not only simplifies manufacturing, but also greatly simplifies inventory and storage problems. A supplier of computer terminals need only stock the basic terminal 10 and maintain a supply of personality modules 22. Since the personality modules are significantly smaller and cheaper than the terminals, a supplier can save space and money by using the terminal of the present invention.

End users can also benefit from the present invention. If one has a computer terminal of the present invention and switches to a different computer system, the user need only replace the personality module with one compatible with the new system. Such a replacement can be effected merely by opening the access door 18, removing the personality module 22 and exchanging it by mail or in person for a different module.

Although only preferred embodiments are specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.

Claims

CLAIMS 1. A computer terminal, comprising: means for displaying information; a base connected with said displaying means; a first circuit board mounted within the base and electronically connected with the displaying means; first microprocessors arranged on the first circuit board for controlling the displaying means in response to signals input to the terminal; a second circuit board removably connectable to the first circuit board so as to be in electronic communication therewith; at least one memory circuit on the second circuit board associated with the first microprocessors, said at least one memory circuit including instructions defining the personality of the computer terminal; and an access door arranged in the base through which the second circuit board may be removed.

2. A method of changing the personality of a computer terminal, comprising the steps of: providing a computer terminal having a base with an access door in it, first microprocessors arranged on a first circuit board arranged within the base, and a personality module which defines the personality of the computer, said personality module being removably connected to the first circuit board; opening the access door; removing the personality module; and plugging a different personality module onto the first circuit board.

3. The computer terminal of claim 1, wherein the at least one memory circuit includes at least one read only memory circuit.

.

4. The computer terminal of claim 3, wherein the at least one read only memory circuit is programmable.

5. The computer terminal of claim 1, wherein the at least one memory circuit stores instructions for determining at least one of a printing font, a character size, a set up parameter and a key function of the terminal.

6. The computer terminal of claim 1, wherein the at least one memory circuit includes at least one random access memory circuit.

7. The computer terminal of claim 1, wherein the first circuit board includes means for controlling a CRT display and means for storing a bit map for the CRT display, the storing means providing information to the controlling means.

8. The computer terminal of claim 7, wherein the storing means is a random access memory.

9. The computer terminal of claim 7, wherein the first microprocessors communicate with the at least one memory circuit simultaneously with the storing means providing information to the controlling means.

10. The computer terminal of claim 7, wherein the storing means stores at least one attribute of characters displayed by the computer terminal.

11. The computer terminal of claim 1, wherein the at least one memory circuit defines one of a plurality of personalities of the computer terminal.

12. The computer terminal of claim 11, wherein the second circuit board includes means for selecting one of the plurality of personalities defined by the at least one memory circuit.

13. A bit-mapped computer terminal for displaying alphanumeric characters having a selectively changeable personality comprising: processing means for controlling the computer terminal in response to signals input to the terminal; first means for storing data defining the personality of the computer terminal, the first storing means being in electrical communication with the processing means; a display for displaying the alphanumeric characters; second means for storing a bit map of the display; means for controlling the display in response to the bit map in the second storing means, the controlling means being in electrical communication with the second storing means; third means for storing at least one of a plurality of attributes of the characters, the third storing means being selectively in communication with the processing means and the controlling means; means for imposing the at least one attribute stored in the third storing means on the bit map; wherein the first storing means is removably connected in the computer terminal.

14. The bit-mapped computer terminal of claim 13, wherein the first storing means includes at least one read only memory circuit.

15. The bit-mapped computer terminal of claim 14, wherein the at least one read only memory circuit is programmable.

16. The bit-mapped computer terminal of claim 13, wherein the first storing means stores instructions for determining at least one of a printing font, a character size, a set up parameter and a key function.

17. The bit-mapped computer terminal of claim 13, wherein the first storing means includes at least one random access memory circuit.

18. The bit-mapped computer terminal of claim 13, wherein the processing means communicates with the first storing means simultaneously with the controlling means communicating with the second storing means.

19. The bit-mapped computer terminal of claim 13, further includes means for selecting one of a plurality of personalities stored by the first storing means.

20. The bit-mapped computer terminal of claim 13, wherein the plurality of attributes include blinking, reverse video and highlighting.