Computer-directed process control system with interactive display functions

Claims

I claim:

1. In an industrial process instrumentation system for use with complex processes having a number of variable process conditions such as temperature, flow rate, and the like, said system comprising:

data processor means arranged to receive signals representing the values of various process conditions, said processor means having data storage means with processor control data stored therein comprising programs and operational base data such as set-point values for performing sequential computations respecting said process conditions so as to produce corresponding output signals for use in controlling the process;

an operating console;

signal transmission means coupling said console to said data processor means to transmit signals thereto and receive signals therefrom;

display means forming part of said console for producing visual images in the form of symbols for inspection by an operator;

memory means storing data signals for controlling said display means, said memory means having a plurality of separate storage locations each adapted to store data signals for establishing the symbolic image in a corresponding position of said display means;

said storage means of said data processor means having data stored therein representing a plurality of sets of display data words to be transmitted over said signal transmission means to said memory means for storage therein to control said display means with each of said sets of display data words defining a respective display presentation symbolically presenting the present status of selected portions of said processor control data respecting at least one corresponding process condition for which computations are being performed by said data processor means and including as part of said presentation preselected symbols identifying display positions where characters may selectively be entered;

memory write in means responsive to said sets of display words received over said transmission means from said data processor means to store in said memory means data signals identifying the selected symbols to be displayed on said display means and stored in memory means storage locations corresponding to display positions where the symbols are to be displayed, thereby to present on said display means for operator inspection the display presentation corresponding to the selected set of display data words transmitted to said console;

manually-operable data entry means coupled to said memory means for inserting therein data signals representing symbols desired to be displayed on said display means;

said data entry means including means operable while any one of said display presentations is presented on said display means to enter into at least one predetermined location in said memory means as identified by at least one of said preselected symbols signals representing changed data for at least a part of said processor control data respecting a particular condition of said process about which information is then presented on said display means responsive to the set of display words received by said memory means from said data processor means, said entered data signal serving to develop a corresponding symbol on said display in a position corresponding to said predetermined location; and

manually-controllable read out means coupled to said memory means to direct said changed data signals entered by said data entry means into said predetermined location of said memory means to said transmission means for transmittal on to said data processor means to alter correspondingly said processor control data for said particular process condition thereby to alter correspondingly the subsequent computations respecting said particular condition, whereby the processing carried out by said processor means is readily controllable by data inserted by an operator into selected locations of said memory means as determined by symbolic information presented on said display means by signals from said central data processor.

2. A system as claimed in claim 1, wherein the selected processor control data presented by said display presentation includes characters representing the set-point value for said particular process condition; and

said data entry means includes means to enter into said one predetermined location of said memory means a signal representing a changed set-point value for said particular process condition for transmittal on to said data processor means to correspondingly alter the set-point value previously forming part of said processor control data for that particular process condition, whereby the subsequent computations for that particular process condition are carried out using the new set-point value.

3. A system as claimed in claim 1, wherein the display presentation includes blank spaces for the entry of new data signals to be transmitted on to said data processor means;

said preselected symbols being located positionally adjacent said blank spaces to indicate to the operator where the new data signals are to be entered.

4. A system as claimed in claim 3, wherein said preselected symbols are horizontal lines appearing as underlines beneath the blank spaces into which new symbols are to be entered by said data entry means.

5. In an industrial process instrumentation system for use with complex processes having a number of variable process conditions such as temperature, flow rate, and the like, wherein the system comprises data processor means arranged to receive signals representing the values of various process conditions, said processor means having storage means with processor control data stored therein comprising program sequences and operational base data such as condition set-point values required for carrying out on a time-sharing basis sequential computations respecting said process conditions to produce corresponding output signals for use in controlling the process; said storage means also having stored therein a plurality of sets of display data words with each set defining the symbols of a visual display to be presented to an operator comprising symbols representing the present status of selected portions of said processor control data respecting at least one of said process conditions for which computations are performed by said processor means, the system further including operating means and signal transmission means coupling said operating means to said data processor means to transmit signals thereto and receive signals therefrom; display means forming part of said operating means for producing visual images in the form of symbols for inspection by an operator; memory means for storing data signals for controlling said display means, said memory means having a plurality of storage locations each adapted to store data signals for establishing the symbol in a corresponding position of said display means; the operating means further having manually-operable data entry means for inserting into said memory means locations data signals representing symbols for presentation on said display means;

the method of operating said instrumentation system comprising the steps of;

transmitting from said processor means through said transmission means to said operating means one of said sets of display data words specifying symbols to be presented in predetermined respective positions on said display means to form a corresponding one of said display presentations and including information symbols representing the present status of selected portions of the processor control data for at least one particular process condition respecting which computations are performed by said processor in accordance with the corresponding processor control data;

storing said display data words in corresponding locations of said memory means;

inserting at least one data signal from said data entry means into a location of said memory means corresponding to a predetermined display position on said display means forming part of said display presentation developed by the set of display words transmitted thereto by said data processor means, said one data signal producing a corresponding symbol on said display means and representing an instruction for the change of data respecting part of the processor control data for said particular process condition;

transmitting from said memory means to said data processor means said one data signal entered by said data entry means in said location of said memory corresponding to said predetermined display position; and

altering the processor control data stored in said processor storage means for said particular process condition in accordance with said one data signal transmitted from said memory means to said central data processor, whereby to alter correspondingly the computational processing respecting said particular process condition in accordance with the instruction represented by said data signal entered in said memory means.

6. The method of claim 5, wherein said data signal entered into said memory means defines a change to be made to the set-point value of said particular process condition;

said processor control data being altered in response to said data signal to identify a new set-point value for said particular process condition.

7. The method of claim 5, wherein said sets of display words transmitted from said data processor means to said operating means include signals producing horizontal lines on said display means to indicate blank spaces where the operator is to insert data signals for transmittal on to said data processor means to alter the processor control data to provide changed computations respecting a process condition.

8. In an industrial process instrumentation system for use with complex processes having a number of variable process conditions such as temperature, flow rate, and the like, said system comprising:

signal processing means arranged to receive signals representing the values of different variable process conditions to be controlled, said signal processing means including data storage means with processing control data stored therein including operational base data such as set-point values for use in carrying out required signal processing respecting said variable process conditions so as to produce corresponding output signals for use in controlling the process condition;

an operating console;

signal transmission means coupling said console to said signal processing means to transmit signals thereto and receive signals therefrom;

display means forming part of said console for producing visual images in the form of symbols for inspection by an operator;

memory means at said console including means storing data signals for controlling said display means, said memory means including a plurality of separate storage locations each adapted to store data signals for establishing the symbolic image in a corresponding position of said display means;

display signal storage means having data stored therein representing a plurality of display data words to be transmitted to said memory means for storage therein to control said display means with sets of said display data words defining respective display presentations symbolically presenting the present status of selected portions of said processing control data respecting corresponding variable process conditions for which signal processing operations are being performed by said signal processing means and including as part of said presentation a preselected location characterizer identifying at least one display position where characters may selectively be entered;

memory write-in means responsive to said sets of display words received from said display signal storage means to store in said memory means data signals identifying the selected symbols to be displayed on said display means and stored in memory means storage locations corresponding to display positions where the symbols are to displayed, thereby to present on said display means for operator inspection the display presentation correponding to a selected set of display data words transmitted to said memory means;

manually-controllable means for operating said display means including data entry means for inserting into said memory means data signals representing symbols desired to be displayed on said display means;

said data entry means including means operable while any one of said display presentations is presented on said display means to enter changed data signals into said memory means for storing in at least one predetermined location in said memory means as identified by said preselected location characterizer symbol signals representing changed data for at least a part of said processing control data respecting a particular condition of said process about which information is then presented on said display means responsive to the set of display words received by said memory means from said display signal storage means, thereby to develop a corresponding symbol on said display in a position corresponding to said one predetermined location; and

means coupled to said transmission means for directing therethrough to said signal processing means signals corresponding to said changed data signals to alter correspondingly said processing control data for said particular process condition thereby to alter correspondingly the subsequent signal processing respecting said particular condition, whereby the processing carried out by said signal processing means is readily controllable by data inserted by an operator into selected locations of said memory means as represented by symbolic information presented on said display means by signals from said memory means.

9. In an industrial process instrumentation system for use with complex processes having a number of variable process conditions such as temperature, flow rate, and the like, wherein the system comprises signal processing means arranged to receive signals representing the values of different variable process conditions to be controlled, said processing means having data storage means with processing control data stored therein comprising operational base data such as process condition set-point values for use in carrying out predetermined signal processing operations respecting said variable process conditions so as to produce corresponding output signals for use in controlling the process conditions; the system further including display signal storage means having stored therein a plurality of display data words with sets thereof defining the symbols of visual display presentations to be presented to an operator including graphic symbols representing the present status of selected portions of said processing control data respecting at least one of said variable process conditions for which signal processing operations are being performed by said signal processing means; the system still further including operating means and signal transmission means coupling said operating means to said signal processing means to transmit signals thereto and receive signals therefrom; display means forming part of said operating means for producing visual images in the form of symbols for inspecting by an operator; memory means including means for storing data signals for controlling said display means, said memory means having a plurality of storage locations each adapted to store data signals for establishing the symbol in a corresponding position of said display means; the operating means further having manually-operable data entry means for inserting into said memory means data signals representing symbols for presentation on said display means at positions corresponding to the storage locations in said memory means;

the method of operating said industrial process instrumentation system comprising the steps of;

transmitting from said display signal storage means a set of display data words specifying symbols to be presented in predetermined respective positions on said display means to form a corresponding one of said display presentations and including information symbols representing the present status of selected portions of the signal processing control data for at least one particular process condition respecting which signal processing operations are performed by said signal processing means making use of the corresponding processing control data;

storing said transmitted display data words in corresponding locations of said memory means;

developing at least one data signal through operation of said data entry means;

entering said one data signal in said memory means for storage therein in a location of said memory means corresponding to a predetermined display position on said display means forming part of said display presentation developed by the set of display words transmitted thereto from said display signal storage means, said one data signal representing information defining a corresponding symbol to be displayed on said display means and identifying a change of data respecting part of the processing control data for said particular process condition;

transmitting to said signal processing means a signal corresponding to said one data signal entered by said data entry means; and

altering the processing control data stored in said data storage means for said particular process condition by substituting a signal corresponding to said one data signal, whereby to alter correspondingly the signal processing operations carried out respecting said particular process condition in accordance with the instruction represented by said data signal developed by said data entry means, the changed data signal stored in said memory means serving to permit the operator to view the changed display presentation on said display means to check it for accuracy.

10. An industrial process instrumentation system for use with complex processes having a number of variable process conditions such as temperature, flow rate, and the like, comprising:

signal processing means arranged to receive signals representing the values of different variable process conditions to be controlled, said signal processing means including data storage means with processing control data stored therein including operational base data such as set-point values for use in carrying out required signal processing respecting said variable process conditions so as to produce corresponding output signals for use in controlling the process condition;

an operating console;

signal transmission means coupling said console to said signal processing means to transmit signals thereto and receive signals therefrom;

display means forming part of said console for producing visual images in the form of symbols for inspection by an operator;

memory means including means storing data signals for controlling said display means and incorporating a plurality of separate storage locations each adapted to store data signals for establishing the symbolic image in a corresponding position of said display means so as to provide for controlling said display means with any of a plurality of sets of display data works defining respective display presentations symbolically presenting a plurality of items of information including the present status of selected portions of said processing control data;

manually-controllable means for operating said display means including data entry means for inserting into said memory means data signals representing information desired to be displayed symbolically on said display means to represent changed data for at least a part of said processing control data respecting a particular condition of said process about which information is then presented on said display means reponsive to a particular set of display words; and

means coupled to said transmission means for directing therethrough to said signal processing means signals corresponding to said changed data to alter correspondingly said processing control data for said particular process condition thereby to alter correspondingly the subsequent signal processing respecting said particular condition, whereby the processing carried out by said signal processing means is readily controllable by data inserted by an operator and stored in selected locations of said memory means as identified by symbolic information presented on said display means.

11. In an industrial process instrumentation system for use with complex processes having a number of variable process conditions such as temperature, flow rate, and the like, wherein the system comprises signal processing means arranged to receive signals representing the values of different variable process conditions to be controlled, said processing means having data storage means with processing control data stored therein comprising operational base data such as process condition set-point values for use in carrying out predetermined signal processing operations respecting said variable process conditions so as to produce corresponding output signals for use in controlling the process conditions; the system further including display signal storage means having stored therein a plurality of display data words with sets thereof defining the symbols of visual display presentations to be presented to an operator including graphic symbols representing the present status of selected portions of said processing control data respecting at least one of said variable process conditions for which signal processing operations are being performed by said signal processing means; the system still further including operating means and signal transmission means coupling said operating means to said processing means to transmit signals thereto and receive signals therefrom; display means forming part of said operating means for producing visual images in the form of symbols for inspection by an operator; memory means including display memory locations adapted to store data signals for establishing the symbols in corresponding positions of said display means; the operating means further having manually-operable data entry means for inserting into said memory means data signals representing information for symbolic presentation by said display means;

the method of operating said industrial process instrumentation system comprising the steps of;

storing in predetermined respective display memory locations a set of display data words to form on said display means a corresponding display presentation and including information symbols representing the present status of selected portions of the signal processing control data for at least one particular process condition respecting which signal processing operations are performed by said signal processing means;

developing through operation of said data entry means at least one data signal representing a change of data respecting part of the processing control data for said particular process condition;

transmitting to said signal processing means a signal corresponding to said one data signal entered by said data entry means to alter the processing control data stored in said data storage means for said particular process condition in accordance with said one data signal, whereby to alter correspondingly the signal processing operations carried out respecting said particular process condition in accordance with the instruction represented by said data signal developed by said data entry means; and

storing in one of said display memory locations a new data signal corresponding to the altered control data to provide the operator with a graphic display of such control data to permit checking for accuracy.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to industrial process control systems of the type including a central processor which functions in a time-share mode to make calculations respecting a large number of variables, such as process conditions, and to produce corresponding information or command signals for a variety of purposes such as positioning process valves or the like. More particularly, this invention relates to such systems having visual display means for presenting to the process operator or process engineer intelligible information to aid such personnel in exercising control over the process.

2. Description of the Prior Art

Computer-operated control systems have been in use for a number of years with various kinds of industrial processes. Such systems generally provide some form of visual data display to aid the process operating personnel, although for the most part the data displays have been relatively rudimentary and only suitable for limited purposes. Experience with such equipment has demonstrated that the process operating personnel require substantially improved facilities for communicating with the control system in order to exercise the desired close and effective control over a process. There have been a number of proposals to provide elaborate data displays with quite large display capacities, such as large-screen CRT devices. However, for various reasons such apparatus provided or proposed heretofore has not satisfactorily solved the problem.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

The computer control system to be described hereinbelow includes an operator's console uniquely designed for use by process operators and engineers. It enables communication with the process and permits rapid and convenient access to information about the process, as well as changes to the control system. The console configuration includes a CRT display, a multi-function keyboard, alarm keys, and may include a trend recorder and a printer. Character positions on the CRT can be identified by a cursor which may be moved to any location on the display by manual controls on the keyboard or by the central processor. The cursor does not displace characters. It is used to point to a location for keyboard modification or program use.

The CRT console permits simultaneous display of related process information. Operator-process interaction can take the form of single or multiple entries onto blank(s) or changeable portions of a display. The console provides a parallel, conversational medium with instructional aids and directory displays.

Inherent in the console system design is the concept of local and computer interaction. That is, an operator may change, write over, or insert characters in unprotected areas of a display without requiring computer servicing and without changing computer memory. The computer is involved as necessary to spend or receive information. Call sequences for displays are designed to permit ease of going from overall summarizing formats to in-depth presentations of a small sector of the control net-work.

All functions and procedures are oriented to a process operator or process engineer. Information is presented in formats appropriate to the process. Operator console functions are designed to be self explanatory, in terms of purpose and procedure. No knowledge of system operation, software structure, or program languages is required to use the console.

Accordingly, it is a principal object of the invention to provide superior industrial process control apparatus of the type having data display means. Another principal object of this invention is to provide improved methods and techniques wherein image display means may be used to significantly enhance a process operator's capacity to control an industrial process and to perform related functions.

Other objects, aspects and advantages of the invention will in part be pointed out in, and in part apparent from, the following description considered together with the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of a process control system;

FIG. 2a is a front perspective view of a CRT console for the system of FIG. 1, and FIG. 2b is an enlarged portion of FIG. 2a showing the alarm keys;

FIG. 3 is a schematic block diagram showing the principal components of the CRT display system;

FIG. 4 is a pictorial illustration of the refresh memory for the CRT display;

FIG. 5 is a timing diagram showing the time relationship between the different display functions;

FIG. 6 shows a keyboard layout for the CRT display console;

FIG. 7 is a pictorial showing of one possible CRT display;

FIG. 8 illustrates a process unit directory display;

FIG. 9 illustrates a process unit display selectable from the display of FIG. 8;

FIG. 10 is a chart to explain certain symbols used in flow diagrams;

FIG. 11 is a procedural flow diagram for the selection of a process unit display;

FIG. 12 is a loop and block display request form;

FIG. 13 shows a typical loop display;

FIG. 14 shows a typical block display;

FIG. 15 is a procedural flow diagram for selecting a loop or block display;

FIG. 16 shows an Add/Revise display form to permit changes to be made to displays from the operator's keyboard;

FIG. 17 is a procedural flow diagram for the function of making a change to a set point in the control system;

FIG. 18a and 18b and 1-3 show additional CRT displays; and

FIG. 19 is a flow diagram representation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, the process control system comprises a central-processing input/output (CP/10) unit 20 in the form of a high-speed digital computer of the general purpose, stored-program type, organized in a timeshare configuration to perform calculations respecting a large number of input signals. The system is more fully described in U.S. Pat. 3,800,288 which has been issued to Russell et al. One group of such input signals is derived from an input multiplexing system 22 arranged to present to the processor a series of measurement signals representing the magnitudes of respective process conditions. In response to such inputs, the processor develops corresponding information or command signals which are directed to various operating elements such as process valves and the like.

The control system also includes one or more operator's consoles 24 (see also FIG. 2a) each of which incorporates a large-screen CRT display device 26 arranged to present alphanumeric characters and other graphic data, including for example, diagrammatic configurations as will be described. The console includes a multi-function keyboard 28 which enables the operator to call up a variety of special displays, and to effectively exercise close control over many aspects of the system. Such console displays can provide continually updated images of total plant functioning, e.g., in terms of raw material inflow and product outflow. The displays may also focus on a process sub-system, individual process unit, control loop, functional block within a loop, or even selected variables. The displays are formatted to provide information as well as to guide the operator in directing the control action of the system. The displays include fill-in-the-blank formats which cooperatively function together with computer software processing to provide the operator with powerful and effective tools for manipulating the process.

Referring now to FIG. 3, the display of the CRT 26 is basically controlled by a conventional refresh memory 30 containing binary data words which define the characters (and other graphic images) to be produced on the screen of the CRT. The stored data words are periodically and sequentially read out through the output lines 32 to an output data buffer 34 which supplies the signals to a character generator 36 (when alphanumeric characters are to be displayed). This character generator produces CRT control signals which are directed through a display multiplexer 38 to the deflection circuits 40 for the CRT 26. The deflection circuits perform digital to analog conversion and operate in the usual fashion to form the display characters on the screen of the CRT.

Although various types of memories could be used, it is preferred to employ a dynamic memory of the semi-conductor type. Access to the stored data can be obtained rapidly and at random, by supplying appropriate addressing codes to the memory address lines. Such memory devices require separate Write and Read control signals, which can readily be developed by associated logic controls.

The refresh memory 30 has a capacity to store 2048 12-bit words, but because of system considerations only 2000 words ordinarily will be stored. When alphanumeric character words are stored in the memory, there is a one-to-one mapping relationship between the memory storage locations and the display locations on the face of the CRT. The CRT screen has a 12 inches .times. 15 inches usable display area, and is arranged to present 2000 alphanumeric characters in 25 lines of 80 characters each. The characters are 0.24 inches high by 0.12 inches wide.

Referring also to FIG. 4, which is a pictorial illustration of the separate storage bins of the refresh memory 30, it will be seen that each of the 2000 storage words contain 12 bits. The last 8 bits define the display character in standard ASCII code. The first 4 bits are for control purposes. Specifically: bits No. 0 and No. 1 together define the display mode as the either alphanumeric or vectorgraphic (to be discussed more fully hereinafter); bit No. 2 is the so-called protect bit, the function of which will be explained hereinbelow; and bit No. 3 determines whether the character is presented steadily or with periodic blinking.

The primary function of the refresh memory 30 is to periodically present to the CRT all of the stored character and/or symbol data, so as to refresh the visual display on its screen at a sufficiently high frequency to avoid flickering. This cyclic operation of the refresh memory occurs at the rate of 60 frames per second, and is controlled by a Display Address Register (DAR) 50 the address signals from which are directed through an address multiplexer 52 to the address lines 54 of the refresh memory. At the start of each frame, the DAR is set to its home or zero address, corresponding to the upper left-hand corner of the CRT display. Thereafter, the DAR is incremented periodically through the remaining 1999 addresses, to read out the associated data words from the memory as the frame time proceeds through its period (1/60 of a second, typically 16.67 milliseconds).

For each address read out from the DAR, there is a corresponding read-out cycle of the refresh memory 30. This operation is called a display-memory-cycle, or DMC, and takes about 1 microsecond. DMCs occur every 4 microseconds, except when the character to be displayed requires more than 4 microseconds of character generator time, in which case the DMCs will be separated by 8 microseconds.

The display memory cycles (DMCs) are interleaved, on a time scale, with other refresh memory cycles referred to as channel-memory-cycles, or CMCs. During these latter cycles, the refresh memory is read or written into in response to command signals from the CP/IO unit 20. This time-sharing of the refresh memory 30 is illustrated in the timing diagram of FIG. 5. The memory cycles DMC and CMC are initiated by corresponding request pulses referred to as display-memory-request (DMR) and the channel-memory-request (CMR), occurring in alternating fashion. Thus, after a DMC has been completed, and while the character generator is busy developing the CRT beam control signals, a CMC can be produced (if requested) to access any address in the refresh memory, to permit data to be written into the memory from the CP/IO unit or to permit data to be read out and transferred to the CP/IO unit.

The protect bit (No. 2) is of special significance in the console operation. When this bit is marked, i.e. a binary one, the associated character is termed a protected character. One feature of a protected character is that it cannot be altered in any fashion by the keyboard 28. Storage locations where the protect bit is a zero can be written into by the keyboard at the will of the operator.

The keyboard 28, outlined in detail in FIG. 6, includes a set of alphabetic keys 60 and a set of numeric keys 62. When the operator presses any one of these keys, a digital code word identifying the character is stored in a keyboard buffer register 66 (FIG. 3). This coded character is directed to an input data multiplexer 68 which transmits it onto the memory input lines 70 to be loaded into the refresh memory 30 at a specified word position, provided that such word position is unprotected. The loading operation takes place during a display memory cycle (DMC), referred to previously.

The word position to be loaded with the keyboard character is identifed on the face of the CRT screen by a movable cursor. Preferably, the cursor is in the form of a small triangular marker located immediately below the identified position. This cursor is produced by the character generator 36 together with any character which already occupies the marked storage position in the memory.

The character generator produces the locator cursor in response to a signal from an output line 72 of a comparator 74. This comparator compares the continuously changing output of the Display Address Register (DAR) 50 with the output of a Cursor Address Register (CUAR) 76 and, when the two are identical, sends a signal to the character generator to develop the cursor image at the CRT display position then identified by the address signals delivered to the memory address lines 54 by the DAR. The CUAR is controllable by special keys 78 on the keyboard, or by CP/IO interaction, so as to permit moving the cursor to any position on the screen.

Before the character in the keyboard buffer register 66 is loaded into the refresh memory 30, the character word already stored in the cursor-identified storage position is examined to determine whether its protect bit is a one or a zero. If a zero, the writing operation proceeds normally. If a one, the control logic circuitry is conditioned to prevent any writing into the memory device during the particular memory cycle (DMC) corresponding to the cursor position.

By these means, certain special words, symbols or numbers, etc., placed in the refresh memory 30 by the CP/IO unit, can be made immume to any alteration from the operatior's keyboard 28. For example, selected headings of columns in a tabular data display, or certain operating parameters of a control loop, can be made effectively permanent, so far as the process operator's console is concerned, and subject to modification only in accordance with strictly defined procedures established in the computer software which, in turn may cause the protect bit of a word in the refresh memory to be changed from a one to a zero.

Although the keyboard 28 can make limited local alterations to the data stored in the refresh memory 30, the display data is primarily controlled by the CP/IO unit 20. Data transfers between the CP/IO unit and the refresh memory, in either direction, take place through a data bus arrangement referred to as Channel Input/Output, or CIO. The transfer operation is initiated at the CP/IO Interface 80 (FIG. 3) which sends through leads 82 a set of control signals specifying details of the transfer. The ensuing data transfers are transmitted from the CP/IO Interface to the Console Controller Interface via lines 82, or from the Console Controller Interface to the CP/IO Interface via lines 96.

In one embodiment, the control signals were for convenience arranged in two standarized-format, serially-transmitted 12-bit words. The first word contained one bit specifying whether the upcoming transfer was to be of the protected or non-protected type. Another bit of the first word specified the Read or Write mode, i.e., indicating whether there was to be a transfer from the refresh memory 30 to the CP/IO unit 20, or a transfer from the CP/IO unit to the refresh memory. The second word contained the starting address of the refresh memory for the transfer, this address being loaded into a Channel Address Register (CAR) 84 (FIG. 3) the output of which is directed to the Memory Address Multiplexer 52 (FIG. 18). As indicated in FIG. 5, this multiplexer time-shares the refresh memory between the Channel Address Register and the Display Address Register 50. The Channel Address Register is incremented by suitable controls to identify successive memory addresses as the transfer operation proceeds after all the control information has been loaded and processed.

The control signals delivered by the Interface 80 are analyzed by logic circuitry in the Console Control Logic Circuitry 90, which includes means for examining specified bit locations of the control words. When the control word is found to specify an unprotected transfer, data is transferred from (or into) each successive memory location identified by the Channel Address Register 84, regardless of whether the words already stored in such locations contain a marked protect bit or not. If a protected transfer is indicated by the control word, data is transferred from (or into) only those storage locations which have unmarked (zero) protect bits. That is, the transfer operation will skip over all protected locations in the specified address field, and will operate only on the unprotected locations, in the sequence in which they are encountered.

Display characters typically are transferred to the refresh memory 30 after the two control words have been processed. The data transferred from the CP/IO unit may provide an entire new display, i.e., the procedure may include erasure of all previous characters and insertion of a complete new set of characters, or writing over some existing characters. In many cases, the new data from the CP/IO unit will represent a response to some action taken