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rfc:rfc296

Network Working Group D. Liddle Request for Comments: 296 Owens-Illinois, Inc. NIC: 8484 January 1972

                        DS-1 DISPLAY SYSTEM

Introduction

 This document describes a proposed modular graphic/alphanumeric
 display system containing a 512 x 512 line, 60 line per inch plasma
 display/memory panel and a mini- processor.  It is intended to
 combine the advantages of display memory and local processing power
 to operate in three general modes as follows:
 1. As an "intelligent terminal" operating on data received from the
    network or a local host to perform text editing, picture
    processing, etc.
 2. As a passive terminal in which the mini-processor translates
    existing display lists, command strings and data structure for
    storage tube terminals or other devices into the proper form to
    operate the plasma display.  In particular, a software module for
    simulation of the ARDS 100A is provided.
 3. As an offline system, where the processor is operated as a stand-
    along mini-computer for debugging, editing, and general display
    work.
 The DS-1 consists of a display module, a processor module, and
 keyboard (see Figure 1).  The display model is a DIGIVUE_
 display/memory unit, model 512-60, produced by Owens-Illinois, Inc.,
 containing the plasma panel and associated drive circuitry.  The
 processor module was specially designed and built for the DS-1
 application by the Raytheon Company.
 A modem is enclosed in the processor module, and is described in
 later sections.  An alternative RS 232 interface is also available
 for connection to a TIP or teletype compatible system.
 [Figure 1 DS-1 Display System*]
 In addition to the display module and the processor, the DS-1 has a
 modem for data transmission, and Ascii keyboard, and an I/0 interface
 to support numerous external devices.  The mechanical design of the
 DS-1 emphasizes flexibility, so that both the keyboard and display
 module can be oriented independently of the processor module.

Liddle [Page 1] RFC 296 DS-1 Display System January 1972

 Software will be supplied with the DS-1, for such functions as text
 editing, vector generation, data management and various I/0 routines.
 The DS-1 is intended principally to operate as an online terminal;
 the offline mode is used for programming and data preparing chores
 which do not require access to the host computer.  In describing
 system operation, therefore, offline operations are simply a subset
 of online operations in which the only I/0 functions are local.  The
 I/0 operations are accomplished by "direct" input/output
 instructions, a special feature of the 700 series machines developed
 at the Raytheon Company.  A single instruction (DIN for input, DOT
 for output) enables the external device addressed by the instruction
 to accept the data presently in the accumulator (DOT) or to transmit
 data to the accumulator (DIN) over the data buss.
 The plasma display X and Y address registers are seen as output
 devices by the processor; the other basic output device is the modem.
 The keyboard and input modem are the basic input devices, in addition
 to the optional cassette tape system for program loading.  These
 devices, and the interfacing of other peripherals are described in
 later sections.
 Figure 2 is a block diagram of the basic DS-1 configurations,
 emphasizing the I/0 structure.  The principal role of the processor
 module is in the restructuring of input data to an appropriate output
 form, either from modem-to-display (computer to operator) or
 keyboard-to-modem (operator to computer).  Such processing consists
 of handling communication chores,
 [Figure 2 US-1 I/0 Configuration*]
 string and stack manipulation, character suppression or translation,
 vector construction from endpoint data or character-encoded line
 drawing commands, and data stream protocol and management, so that
 the input/output character stream over the modem or channel remains
 compatible with the host computer, while the keyboard inputs and
 display outputs are being effectively and efficiently handled.
 The real significance of the DS-1 as a new display terminal stems
 from its use of the plasma display/memory unit.  Because of its
 inherent memory and selective erase capability, it can be addressed
 asynchronously, requires no special "refresh" or access to buffer
 memory, and is indistinguishable from any other output medium, such
 as tape, etc.  Seen from the operator's point of view, it has very
 desirable human factors, such as high contrast and "crisp" line
 dimensions, no jitter, flicker, or distortion, and the capability for
 rear projection of pictorial or tabular data from slides or
 microfiche, for example.

Liddle [Page 2] RFC 296 DS-1 Display System January 1972

 Both the display module and the processor are described in details in
 subsequent sections, as well as the mechanical construction,
 communication interfaces, keyboard, and the system software.
 Section 2. Display Module
 The DS-1 display module is an Owens-Illinois DIGIVUE_ display/memory
 unit Model 512-60.  It contains the plasma panel, drive electronics,
 and display logic.  These three assemblies are described in the
 following paragraphs.
 PANEL
 The DIGIVUE_ display panel (or plasma panel) is a matrix device.  It
 is constructed from two pieces of 1/4" plate glass, upon which very
 fine gold electrode lines are deposited.  These electrodes are then
 completely covered by a dielectric film.  These two plates are then
 sealed together with a gap of a few thousandths of an inch between
 them, and with their electrode patterns orthogonally oriented.
 This "sandwich" is then baked out and pumped down to high vacuum,
 backfilled with a gas mixture consisting largely of Neon, and sealed
 off.  The addition of flexible ribbon cable connectors completes the
 fabrication of the panel.  The device is fat, roughly _" thick, and
 virtually transparent.
 The panel is operated in such a way that any location (i.e., any x, y
 intersection) may be individually turned "on" or "off" as a source of
 visible light.  Further, such a location has a "memory" and is
 sustained in the 'on" or "off" state until a new selection signal
 changes it.
 An AC voltage is applied between all x and all y electrodes in
 parallel, so that an AC signal less than the breakdown potential is
 applied across the gas at all times.  This is called the sustaining
 voltage, VS.  When a single x,y point is to be addressed, a voltage
 pulse, VP, is applied to the appropriate x and y lines, such that the
 total addressing voltage at their intersection is given by
                           V ADD = VS + 2VP,
 which exceeds the breakdown potential of the gas, initiation a
 discharge.
 Since the electrodes are covered by a dielectric, no discharge
 current can flow in the external circuit.  Rather, the ions and
 electrons produced by the discharge are carried by the applied field
 and are deposited as stored charge on the dielectric surfaces, until

Liddle [Page 3] RFC 296 DS-1 Display System January 1972

 the resultant net field is nearly zero, quenching the discharge after
 about one microsecond.  As the AC sustaining voltage changes
 polarity, however, this stored charge constitutes a bias voltage,
 adding to the sustaining signal and producing a new discharge, which
 results in stored charge causing another discharge on the next half
 cycle, etc.  Thus, once addressed, a single x,y location continues to
 produce a discharge twice in every sustainer period, or about 100
 thousand times per second.  Naturally, this appears as a continuous
 glow to the eye.  A sustained location may be turned off by
 addressing in such a way that the stored charge is allowed to return
 to zero.  Thus, a location, or 'cell", may be turned on or off in a
 bistable, random access manner.
 The plasma display has a number of extremely useful visual
 characteristics.  Its transparency permits the use of rear-projected
 data from microfilm, color slides, maps, forms, etc., to be "mixed"
 with the dynamic, computer generated data to be displayed
 (characters, plots, graphics, etc.). In addition to the high
 brightness of the gas discharge, the contrast ration is extremely
 nigh.  The panel used in the model 512-60 has 512 x 512 lines at 60
 lines per inch.  This high resolution and large size allows highly
 readable characters and graphics to be mixed, without distortion or
 jitter of the data.  Dot matrix characters are especially attractive,
 since the "dots" of the discharge sites have very clean, crisp
 dimensions.
 A significant system characteristic of the plasma display matrix is
 its random access memory property.  Unlike storage tube displays, it
 may be selectively erased as well as written, changing a single
 point, curve, or character without altering the contents of other
 locations on the panel.  Large quantities of text, time histories of
 measured data, or complex memory.  This allows more efficient use of
 the processor and simpler data management within computer memory.
 The 512-60 panel used in the DS-1 application will have an active
 area of 8.5 x 8.5 inches, containing 512 x 512 lines.  There will be
 an additional 4 line peripheral border around the addressable area to
 provide conditioning of the discharge sites.
 The back of the panel will be frosted with an optically diffusing
 surface suitable for the projection of optical images.  A
 circularly-polarizing neutral density filter with anti-glare coating
 will be provided on the front of the display.  The brightness and
 contrast will be sufficient for use in a normal lighted laboratory
 area.

Liddle [Page 4] RFC 296 DS-1 Display System January 1972

 Drive Electronics
 The Drive electronics for the display module will be the standard
 Owens-Illinois circuits requri3ed to operate a 512 x 512 line panel
 as part of our model 512-60 standard display unit.  They consist of a
 sustaining generator, which maintains cells, once addressed, in the
 appropriate state ("on" or "off") after removal of the addressing
 signal, and pulse-forming circuits for the generation and appropriate
 mixing of addressing pulses at the selected panel sites.
 The sustainer will operate with a basic period of 20 microseconds,
 with a peak voltage of approximately 130 volts.  Exact voltage
 levels, frequency and waveshape are adjusted for optimal performance
 subject to power supply constraints and data rate requirements.
 The address circuits are multiplexed to reduce the number of active
 circuits required and employ a non-linear mixing scheme for line
 selection.  A pulse of 100 volts is applied with the proper time
 phase to achieve writing and erasing.  The pulse is disabled in all
 but the selected line pair.
 Provision is also made for bulk erasure in which the entire panel is
 erased in two sustainer periods.  A power supply of high density
 design will provide the necessary sustaining, addressing, and logical
 level voltages.  The design will employ high-frequency invertors and
 switching regulation for maximum efficiency and reduced size.  It
 requires about 250 watts, and will be housed inside the processor
 module.
 Display Logic
 The logic included in the display module provides the timing and
 control required for the sustaining generator and the address pulses,
 and also provides the logic level interface to the processor module.
 The interface is TTL compatible.  It contains 2 nine-bit address
 ports X0-X8 and Y0-Y8, which [not legible*], in absolute binary code
 the x,y intersection which is to be addressed.  These addresses are
 accepted when given a write command or an erase command by the
 control lines W or E, respectively.  These inputs must all be held
 steady until acceptance of the data and completion of the operation
 has been indicated by the status line, a logic level output from the
 display unit.  Ad additional control line, B, is used in conjunction
 with the H line to cause a bulk erasure of the entire screen.

Liddle [Page 5] RFC 296 DS-1 Display System January 1972

 The model 512-60 display unit proposed in this document is of the
 serial address type, and thus can write or erase a single point each
 20 u/seconds.  This permits vectors to be drawn at more than 800
 inches/second.  Characters in a 5x7 dot matrix can be written at a
 rate of about 1400 characters per second.
 A parallel address type display unit is presently being developed at
 Owens-Illinois.  This module, when available, will be compatible with
 the DS-1 system with no modification to the processor required.  This
 display will address 16 lines in parallel, which will allow more than
 6,000 characters per second to be displayed, or a complete page to be
 generated in .330 seconds.
 Section 3 Processor Module
 The Processor is a minicomputer (Figure 1) that accepts ASCII encoded
 commands and generates outputs to control the writing of information
 by the display module.  The Processor performs the functions of
 storing information, data and instructions and regulating the flow of
 information between the terminal's Keyboard, Modems, Display Module,
 and Program Loading Device (Figure 2).
 In a typical operation, the processor calls up input commands from
 the modem and the keyboard and generates instructions to the display
 module driver circuitry to produce the required characters, vectors,
 or editing programs.
 Instructions and data are stored in 16 bit words.  Arithmetic
 functions are performed in 2's complement form.  The basic machine
 cycle time is 1.6 microseconds.
 The major functional units of the processor are: (Figures 3 & 4)
 o  Memory
 o  Memory Address Register
 o  Program Counter
 o  Instruction Register
 o  Accumulator
 o  Instruction Processing Synchronizer
 o  Terminal I/O Circuitry
 These units are briefly described next.

Liddle [Page 6] RFC 296 DS-1 Display System January 1972

 Memory
 An operational memory of 2048 - 16 bit words plus bootstrap memory of
 64-16 bit words are provided.  The 2038 word memory is a Random
 Address Memory (RAM) and is used to store the character generator,
 the vector generator, and the editing programs needed to provide the
 specific operational requirements of the terminal.  Using the RAM
 type memory provides the flexibility
 [Figure 3 Processor Data Flow*]
 [Figure 4 Instruction Processor Synchronizer*]
 to alter instruction routines and to tailor the terminal for the
 application.  Since the terminal uses RAM, an operational program
 loading device (a magnetic tape cassette read/write recorder) is
 proposed so that the operational program can be loaded when the
 terminal is turned on.
 The RAM size is sufficient to permit storage of 128 characters, a
 vector generation routine and an instruction set.
 The bootstrap memory is provided for storing a terminal start up
 program that puts the terminal in a state for reading instruction
 data into its operational memory from external sources.  Read Only
 Memory (ROM) devices are used for the bootstrap memory.  Both the RAM
 and the ROM memories are made up entirely of MOS.
 Memory Address Register
 The Memory Address Register (MA) is a twelve bit register that can be
 loaded with the program counter or the address portion of the memory
 data.
 Program Counter
 The Program Counter (PC) is a 12 bit counter-register that can be
 loaded with the address portion of the instruction register.
 Instruction Register
 The Instruction Register (IR) is a 16 bit register of which 4 bits
 contain the instruction and 12 bits the data associated with the
 instruction.  This can be loaded with a 16 bit memory word.

Liddle [Page 7] RFC 296 DS-1 Display System January 1972

 Accumulator (AC)
 The Accumulator (AC) is a 16 bit shift register that can be loaded
 with the contents of the program counter, the data inputs, or the
 arithmetic unit.
 Instruction Processing Synchronizer (IPS)
 The Instruction Processing Synchronizer controls the timing and data
 flow in the processor.  Clocked by its own oscillator, the IPS calls
 up instructions from the memory, which then dictates the sequence to
 be followed.
 Terminal I/O Circuitry
 The processor communicates with the other elements of the terminal
 either directly on the I/O bus or via one of three device
 controllers.  The controllers are required to make the I/O devices
 compatible with the processor.  Separate controllers are provided for
 Keyboard, Display Module, and Serial I/O devices.
 The I/O Bus includes:
 o  16 Parallel Input Data Lines
 o  16 Parallel Output Data Lines
 o  4 lines for selecting the I/O device to communicate with the
    processor
 o  4 Lines for specifying the function to be performed
 o  16 sense lines for monitoring the status of each I/O device
 o  2 strobe lines to initiate the transfer of data to and from the
    I/O devices
 o  1 system clock line
 Each of these lines are available at the I/O Bus Connector.  The
 lines required by each controller varies with the function performed
 by the controller (Figure 4).  Three ports are provided with the
 Serial I/O Channel Controller, two asynchronous and one synchronous.
 The latter is for use with an optional cassette tape recorder that
 can be either supplied as an option with the terminal or purchased at
 a later date.  The two asynchronous ports are for interface with a

Liddle [Page 8] RFC 296 DS-1 Display System January 1972

 teletypewriter modem (not supplied) and a telephone modem that is
 supplied with the terminal.  Direct connection with a data processing
 machine ca be accomplished at the I/O bus connector.
 The processor provides a single level interrupt that causes the
 processor to transfer control to a designated sub-program while
 automatically storing the contents of all appropriate registers and
 the return linkage.  The mask and unmask instructions cause the
 interrupt line to be gated according to the state of an inhibit
 flip-flop.  The last instruction (Interrupt Return) restores the
 program counter, accumulator, and overflow indicator to the condition
 existing at the time of interrupting.
 Software
 The desired terminal operations, that is, the logical capabilities of
 the display terminal will be implemented in software.  This approach
 provides a degree of flexibility and versatility to the terminal's
 editing and display writing capability.  In the latter area, the
 generation and display of characters, symbols, and graphics are
 limited in variety only by the resolution (60 dots per inch) and the
 size (8-1/2" x 8-1/2") of the display screen.  The flexible nature of
 this approach is enhanced by the expandability of the memory to 4K
 (32K optional).
 The software is divided into two segments: (1) servicing routines for
 the input modem, the output modem, the keyboard, and the display
 module and (2), specific function routines for line generation,
 editing, point generation, and character generation.
 Typical software processing starts with the program in an idle loop
 checking the input sense line.  When a bit is ready in the modem, the
 sense line goes true, the processor skips and the program inputs the
 bit.  The sense line resets.  The program counts the bit, saves it,
 and returns to an idle loop waiting for subsequent bits.  As each bit
 is input, it is stored in proper sequence.  When a word is entirely
 memory, it is moved to another memory location where it can be
 decoded.  The program resets the input, counts for the next word, and
 transfers to the task routine which analyzes the command and
 determines which segment of the program is to perform the function.
 For this case, assume that the program was instructed to plot a
 character.  The program computes a table from the value of the
 character code.  The table contains a compacted image of the dots
 representing the character.  The image is unpacked from the table
 into a temporary hold area.  Then, starting at the top left corner,
 the program outputs the coordinates and the one or zero value of the
 image.  The next point is output in the next lower Y position.  The

Liddle [Page 9] RFC 296 DS-1 Display System January 1972

 process is repeated until 14 bits have outputted (one column).  The
 program resets the Y coordinate to the original Y and increments the
 X.  The next column is output the same as the first.
 When nine columns have been output, the program returns to the idle
 loop.
 Instruction Description
 Instructions and data are in the form of 16 bit words.  Arithmetic
 functions are performed in 2's complement form.  The following word
 formats are applicable:
 Instruction              0  1  3  4     15
                          I   OP    Address
 Address Data             0  1           15
                          I     Address
 Data                     0 1            15
                          S      Data
 The instruction format provides 1 bit to indicate indirect
 addressing, 3 bits for the operations code (OOP) and 12 bits for the
 address.  The address data format contains 15 bits of address and 1
 bit for indicating indirect addressing.  The data word format
 includes 1 sign bit and 15 bits for data.
 Logical control of data flow in the display processor is centered
 about the accumulator, with the majority of the operations involving
 it, or the sensing of data conditions involving the accumulator.  The
 19 processor operations represent 6 types of instructions:
 o  Data Movement (Through the accumulator)
 o  Logical operations (on accumulator contents)
 o  Condition Checking
 o  Input/Output
 o  Jump Control
 o  Indexing
 Each of these instruction types are briefly discussed next.  Refer to
 Appendix I for a complete description of the instruction set.

Liddle [Page 10] RFC 296 DS-1 Display System January 1972

            Data Movement Instructions - CLA, LDA, ADD, STC
 These four instructions: enable the accumulator to be cleared or to
 be loaded with data; effect the addition of a word to the
 accumulator's contents; and enable the accumulator contents to be
 stored in memory.
                Logical Operations - AND, CMP, RAL, SAL
 These four instructions: enable a word in memory to be logically
 "anded" to the accumulator; permit the 2's complement of the
 accumulator's contents to be formed; enable a left rotation of the
 accumulator contents, and permit a left shift of the accumulator's
 contents to be made.
             Condition Checking - SAZ, SNZ, SAC, SNA, SNO
 These five instructions allow for various condition checks.  SAZ and
 SNZ permit the accumulator to be checked for zero or non-zero
 contents.  SAG and SNA enable any bit position in the accumulator to
 be checked for a 1 or 0 setting.  SNO provides a check for
 accumulator overflow.
                      Input/Output - SS, DIN, DOT
 The SS instruction provides a means of determining whether devices
 which interface with the processor (e.g., modem display module) are
 ready for data transfers.  Actual transfer of data occurs through the
 accumulator, one word at a time.  DIN causes one 16-bit word to be
 transferred from an external device to the accumulator.  DOT
 indicates the transfer of one 16-bit word from the accumulator to an
 external device.  The particular device DIN or DOT address is
 indicated by the value in the device address field of the
 instruction; the instructions enable controller I/O with a variety of
 peripheral units.
                        Jump Control - JMP, JSR
 These instructions provide the means for altering the flow of program
 logic.  JMP is an unconditional transfer of control to a designated
 memory location.  JSR provides a subroutine capability to the
 program.  The execution of a JSR instruction involves saving the
 return address to the jump at a designated location.  By designating
 the store for the return address as not being in line with executed
 code, the program which is in execution can be held in read only
 memory.
                            Indexing - IAS

Liddle [Page 11] RFC 296 DS-1 Display System January 1972

 These instructions provide an indexing facility to the order code.
 The indexing occurs in the memory location specified in the address
 field of the IAS instruction; thus, multiple indexing is possible.
 The above instruction types provide a fundamental but general
 programming capability.  A basic symbolic assembly language has been
 built about this instruction set and is used to write programs which
 do character, assembler program; the assembler is written in FORTRAN
 language.
 Modem
 The display terminal is supplied with a modem for interfacing the I/O
 controller with a telephone line.  The modem operates asynchronously
 through one of the three I/O controller ports (Figure 5).  It is an
 FSK unit that operates at data rates from 0 to 1800 bps in a four
 wire full-duplex mode and from 0 to 1200 bps in a half-duplex mode.
 In the four wire full-duplex mode, both the local and remote modem
 operate fully independently.  A data transfer sequence may be
 originated from either model at any time by activating the Request To
 Send signal.  The data transfer sequence is terminated by dropping
 the RTS signal at the originating modem.  In the half-duplex mode,
 the modem operates with any data format.  Selection between transmit
 and receive modem identity is determined by the status of the Request
 To Send signal from the processor.
 The modem may be used over a dial-up network using the half-duplex
 mode.  Operation in this manner requires the use of the November,
 1968, Data Access Arrangement, number F-57951, supplied by the Bell
 System.  In this operating mode, a data call is originated by the
 phone set associated with the Data Access Arrangement.  At the remote
 location, the call is manually answered and the data key on the phone
 se is placed in the data position.
 Keyboard
 A multimode keyboard with standard ASCII character-to-key assignments
 is proposed.  The keyboard includes codes for upper and lower case
 alphanumerics and special function keys and codes for editing
 operations.
 [Figure 5 DS-1 I/O Data Lines*]
 Section 4 Mechanical Considerations
 The DS-1 consists of three separate self-contained sub-units: the
 display module, the processor module, and the keyboard.

Liddle [Page 12] RFC 296 DS-1 Display System January 1972

 Display Module - The Display Module will contain the plasma panel and
 the driver electronics.  It's overall size will 14" W x 14" H x 61/2"
 D, and will weight approximately 25 pounds.  An 8-1/2" x 8-1/2"
 viewing area will be provided.
 Interconnections to this unit will be provided at the rear of the
 assembly.
 Processor Module - The processor enclosure will contain circuit board
 assemblies, three separate power supplies, and a cassette tape
 recorder (optional).  The overall size of this unit will be
 approximately 20" W x 6-1/2" H x 26" D and will weigh approximately
 60 pounds.
 Input/Output connectors will be provided at the rear of the enclosure
 to accommodate the units with which it must interface.
 Keyboard - This unit will provide a full alphanumeric keyboard housed
 in a desk top enclosure approximately 15" W x 3" H x 7" D.  The unit
 will include:
 o  The entire displayable character set in the standard ASCII layout.
 o  Special Function keys for editing and I/O control.
 Keyboard operation is similar in touch characteristics to an electric
 typewriter and suitable for use by an inexperienced operator.
 Appendix I
 DS-1 Instruction Set The following instructions are provided;
 The execution item for instructions having indirect addressing
 (optional with instruction marked*) requires one cycle for each
 indirect level.
 LDA, A, I Load Word      0  1  2  3  4      15
                          I  0  0  0      A
 This instruction loads the contents of address A into the
 accumulator.  The previous contents are lost.  The program counter is
 indexed by 1.
                            Time = 1 cycle*
                          0  1  2  3  4      15
 JMP, A, I, Jump          I  0  0  1      A

Liddle [Page 13] RFC 296 DS-1 Display System January 1972

 This instruction causes program control to be transferred to the
 address A.  The contents of the accumulator are not altered.
                            Time = 1 cycle*
                          0  1  2  3  4      15
 JSR, A, I, Jump & Save   I  0  1  1      A
                 Return
 This instruction stores the present address plus 1 at the location
 specified by the contents of memory location A and transfers program
 control to location A+1.  The accumulator is cleared.
                            Time = 3 cycles*
                          0  1  2  3  4      15
 ADD, A, I, Add           I  0  1  0      A
 This instruction adds the contents of memory at location A to the
 accumulator.  The overflow indicator is set to the appropriate state
 and remains set until the next ADD, IAS, or CLA instruction is
 processed.
                            Time = 2 cycles*
                          0  1  2  3  4      15
 AND, A, I And            I  1  0  0      A
 The instruction ands logically the contents of the accumulator with
 the data stored in Location A.  The results is stored in the
 accumulator.
                            Time = 2 cycles*
                          0  1  2  3  4      15
 STA, A, I Store          I  1  0  1      A
         Accumulator
 This instruction stores the contents of the accumulator in memory
 Location A.
                            Time = 2 cycles*
 IAS, A, I Index & Skip   0  1  2  3  4      15
           If Zero        I  1  1  0      A
 This instruction reads the contents of memory location A and adds 1
 to it.  The results are then stored back in location A of the memory.
 If the results of the addition is zero (i.e., an overflow generated)
 the next instruction is skipped.  Otherwise, the next instruction is
 executed.  The accumulator contains the contents of A plus 1.

Liddle [Page 14] RFC 296 DS-1 Display System January 1972

                            Time = 3 cycles*
                          0  1  2  3  4  5  6  7  8   11  12  15
 SAL, N Shift             0  1  1  1  0  0  0  0    n
 Accumulator Left
 This instruction shifts the contents of the accumulator left by n
 bits, the least significant bits become zero.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8   11  12  15
 RAL, N Rotate            1  1  1  1  0  0  0  0    n
 Accumulator Left
 This instruction rotates the contents of the accumulator left by n
 bits.  The most significant bit becomes the initial least significant
 bit.
                            Time = cycle*
                          0  1  2  3  4  5  6  7  8    15
 HLT, Halt                0  1  1  1  1  0  0  1
 This instruction causes program execution to stop.  Used primarily
 for debugging purposes, depression of the RUN button or SINGLE CYCLE
 button causes continued execution either continuous or one cycle
 respectively.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8    15
 SAZ Skip Accumulator     0  1  1  1  0  1  0  0
 Zero
 This instruction causes the next instruction to be skipped if the
 accumulator is zero.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8    15
 SNZ Skip Accumulator     1  1  1  1  0  1  0  0
 Non-Zero
 This instruction causes the next instruction to be skipped if the
 accumulator is non-zero.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8  11  12  15
 SAC, B Skip              1  1  1  1  0  1  0  1    B
 Accumulator

Liddle [Page 15] RFC 296 DS-1 Display System January 1972

 This instruction causes the next instruction to be skipped if bit
 number B is one (1).  The most significant bit is zero and the least
 significant is 15.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8    15
 SNO Skip No                 1  1  1  0  0  0  0
 Overflow
 This instruction causes the skipping of the next instruction if the
 overflow is not set.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8    15
 CMP Complement              1  1  1  0  0  1  1
 Accumulator
 This instruction stores the 2's complement of the accumulator in the
 accumulator.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8  11  12  15
 DOT Data Output             1  1  1  0  0  0  1   Add    Func.
 This instruction causes the contents of the accumulator to be gated
 to the DIO Data buss and a Data Output Strobe (DOS) pulse to be
 transmitted to the peripheral device.  This pulse is used by the
 device to store the contents of the Standard I/O Buss.  The device
 Address and Function data is transmitted simultaneous with data.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8  11  12  15
 DIN Data Input              1  1  1  1  1  0  0   Add    Func.
 This instruction causes the device address and function data to be
 transmitted as in the DOT instruction.  Upon detection of this
 address, function and DATA Input Strobe (DIS), the device gates its
 data onto the Standard I/O Buss.  The deactivation of the Data Input
 Strobe indicates that the data has been received and stored.
                            Time = 1 cycle*
                  0  1  2  3  4  5  6  7  8  9  10  11  13  14  15
 INR Interrupt    0  1  1  1  1  1  1  1  0  0   0     L    0    0
 Return

Liddle [Page 16] RFC 296 DS-1 Display System January 1972

 This instruction causes the Program Counter, the Accumulator, and the
 Overflow indicator to be restored to the conditions prior to
 servicing the present active level.  Parameter L must be set to the
 level being processed for correct return linkage.  The interrupt is
 returned to the idle state.  See pages 3-3 and 3-4.
                            Time = 4 cycles*
                          0  1  2  3  4  5  6  7  8    15
 MSK Mask Interrupts      1  1  1  1  1  1  1  0
 This instruction causes the interrupt system to be inhibited from
 causing any interrupt to be processed.  Interrupts waiting or
 received while interrupts are _masked_ will be processed when they
 are unmasked.  See pages 3-3 and 3-4.
                            Time = 1 cycle*
                          0  1  2  3  4  5  6  7  8    15
 UNM Unmask Interrupts    0  1  1  1  1  1  1  0
 This instruction causes the interrupt system to be processed in the
 normal manner.  See pages 3-3 and 3-4.
                          Time = 1 cycle*
  • Please see the PDF file for figures and missing text (not legible in

the original).

Liddle [Page 17]

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