Reference / Paper · 1968
The HP Journal issue introducing the 9100A: Osborne on the hardware (CRT display, inductive printed-circuit ROM, core-rope control ROM, core memory), Cochran on the internal programming (number representation, CORDIC-style trigonometry, logarithms), Monnier and Near.
HEWLETT-PACKARDJOURNAL The HP Model 9100A Computing Calculator SEPTEMBER1968 © Copr. 1949-1998 Hewlett-Packard Co. Fifty years ago this Marchant calculator was touted as The Last Word in Calculators.' Indeed it was! It was the culmination of a history in which many agonies are recorded. For instance, in 1842 Babbage found his funds cut off during the development of a sophisticated 'Ana lytical Engine.' To raise more, he and his friend Lady T H E P O N Y Lovelace played the horses. They lost and the machine was never completed. Then came Thomas Hill in 1857 who forgot that 'bodies set in motion tend to remain in motion.' His 'Arithmometer' was accurate to within a few spins of the digit wheels. Some machines were too slow. An experienced ac countant could add figures in his head faster than some of the machines proposed. A former bank clerk, Wm. Seward Burroughs, made the first practical calculator in 1872. D. E. Felt, in 1879 began selling a machine he called the 'Comptometer.' A 'Multiplier' developed by E. D. Barbour in 1872 was based on the famous 'Napier's bones' principle. Automatic, motor driven models began to appear in the 1920's when, in the U.S., Burroughs, Monroe, Marchant and Friden became recognized standards. In addi tion to the four basic operations of add, subtract, multiply and divide, some of these machines include square root. Electronic desktop calculators first made their appear ance about 5 years ago. There are various sizes, capa bilities and modes of operation. Although more expen sive than the mechanical calculators, they are quiet, fast, versatile and virtually maintenance free. Now we have a new, more powerful desktop calcu lating device. Our Model 9100A is more a computer than a calculator. It may very well be the 'First Word' in a new breed of calculating machines. Laurence D. Shergalis PRINTED IN U.S.A. CHEWL © Copr. 1949-1998 Hewlett-Packard Co. A New Electronic Calculator with Computerlike Capabilities By Richard E. Monnier MANY OF THE DAY-TO-DAY COMPUTING PROBLEMS faced by scientists and engineers require complex calculations but involve only a moderate amount of data. Therefore, a machine that is more than a calculator in capability but less than a computer in cost has a great deal to offer. At the same time it must be easy to operate and pro gram so that a minimum amount of effort is required in the solution of typical problems. Reasonable speed is necessary so that the response to individual operations seems nearly instantaneous. The HP Model 9100A Calculator, Fig. 1, was devel oped to fill this gap between desk calculators and com puters. Easy interaction between the machine and user was one of the most important design considerations during its development and was the prime guide in mak ing many design decisions. CRT Display One of the first and most basic problems to be resolved concerned the type of output to be used. Most people want a printed record, but printers are generally slow and noisy. Whatever method is used, if only one register is displayed, it is difficult to follow what is happening during a sequence of calculations where numbers are moved from one register to another. It was therefore decided that a cathode-ray-tube displaying the contents of three registers would provide the greatest flexibility and would allow the user to follow problem solutions easily. The ideal situation is to have both a CRT show ing more than one register, and a printer which can be attached as an accessory. Fig. 2 is a typical display showing three numbers. The X register displays numbers as they are entered from the keyboard one digit at a time and is called the key board register. The Y register is called the accumulator since the results of arithmetic operations on two num bers, one in X and one in Y, appear in the Y register. The Z register is a particularly convenient register to use for temporary storage. Numbers One of the most important features of the Model 9100A is the tremendous range of numbers it can handle without special attention by the operator. It is not nec essary to worry about where to place the decimal point to obtain the desired accuracy or to avoid register over flow. This flexibility is obtained because all numbers are stored in 'floating point' and all operations performed using 'floating point arithmetic] A floating point number is expressed with the decimal point following the first digit and an exponent representing the number of places the decimal point should be moved — to the right if the Fig. 1. (le(t) This new HP Model 9100A Calculator is sell-contained and is capable of performing functions previously pos sible only with larger computers. Fig. 2. (right) Display in fixed point with the decimal wheel set at 5. The Y register has re verted to floating point because the number is too large to be properly displayed unless the dig its called for by the DEC IMAL DIGITS setting is reduced. © Copr. 1949-1998 Hewlett-Packard Co. R U N o s If Cashing or no display after 30 sec. PRESS: ENTER A NUMBER: • 0 0 Keyboard entries displayed Any operation terminates * < C U M I Red light indicates illegal operation as Sin"'2. \'-x . or division by 0 Up to ten Power of significant digits ten multiplier 5 or i 4 s •;;;• F P X C D - O f l / 5 Aheel sets number of places to right of decimal (here 4). Rightmost digit rounded. Registers with left over flow revert to floatin CONTROL AND ARITHMETIC KEYS PROGRAM OPERATION PRESS: ¿V^i JgJlEf From keyboard: SET: [PROG]~ depress keys in program sequence. From magnetic card: Insert card. PRESS: ENTER TO RECORD A PROGRAM SET: i I BUM I PRESS: i" "i,- (fjïïj£! ditional branch to address given by next two program steps or keyboard entries. CONDITION MET Branches to address given by next two program steps if first step is alphameric. (GO TO not necessary.) Otherwise, executes instructions in next two steps and continues with third step. CONDITION NOT MET Insert magnetic card. PRESS: RECORD TO RUN A PROGRAM SET RUN PRESS - |g£« Skips next two program steps. Continues with third program step (IF FLAG clears the flag ) Sets a condition to be tested by the next IF FLAG May be used manually or as a program stepForces a brief display during pro gram execution. When held down. causes STOP at next prog PAUSE CODE KEY CODE KEY Stops program execution when used manually or as a program step. Ends recording on magnetic card Gives STOP and automatic GO TO (0) (0) Must be last program step. Starts program execution at pre sent address. May be used as a "No Operation" step in PROG mode: Displays address and instruction code m X. - Ã-D _ 13 «-Code .¡N mode. Executes one prostep or all 3 steps of GO TO ( ) ( ). A met "IT" step branches to address in next two steps. II not an address, executes first step only A not met "IF" step branches to and executes third step the DECIMAL DIGITS setting to 4 or less. If the number is too big for the DECIMAL DIGITS setting, the register involved reverts automatically to floating point to avoid an apparent overflow. In FIXED POINT display, the number dis played is rounded, but full significance is retained in storage for calculations. To improve readability, O's before the displayed number and un-entered O's following the number are blanked. In FLOATING POINT, digits to the right of the decimal are grouped in threes. Pull-Out Instruction Card A pull-out instruction card, Fig. 3, is located at the TO CHANGE A PROGRAM STEP front of the calculator under SET: "fSotri PRESS. Desired ke7~^ the keyboard. The operation CODE KEY CODE KEY CODE KEY of each key is briefly ex ' I 9 plained and key codes are • e nou f j • a j *-»{I listed. Some simple examples i.,-. b jC'i are provided to assist those / d using the machine for the first time or to refresh the memory of an infrequent Fig. the Pull-out instruction card is permanently attached to the calculator and contains key codes and operating instructions. user. Most questions regard ing the operation of the exponent is positive, or to the left if the exponent is Model 9100A are answered on the card. negative. Data Entry 4.398364291 X 101 = .004398 364 291. The operator may choose to display numbers in The calculator keyboard is shown in Fig. 4. Num FLOATING POINT or in FIXED POINT. The bers can be entered into the X register using the digit FLOATING POINT mode allows numbers, either posi keys, the * key or the ENTER EXP key. The ENTER tive or negative, from 1 x 10 '"' to 9.999 999 999 x EXP key allows powers of 10 to be entered directly which 1 0"" to be displayed just as they are stored in the machine. is useful for very large or very small numbers. 6.02 X The FIXED POINT mode displays numbers in the 1 0" is entered Q Q O © t I O • If the ENTER way they are most commonly written. The DECIMAL EXP key is the first key of a number entry, a 1 is auto DIGITS wheel allows setting the number of digits dis matically entered into the mantissa. Thus only two key played to the right of the decimal point anywhere from 0 strokes © Q suffice to enter 1,000,000. The CHG to 9. Fig. 2 shows a display of three numbers with the SIGN key changes the sign of either the mantissa or the DECIMAL DIGITS wheel set at 5. The number in the Y exponent depending upon which one is presently being register, 5.336845815 x 10 = 533 684.5815, is too addressed. Numbers are entered in the same way, regard big to be displayed in FIXED POINT without reducing less of whether the machine is in FIXED POINT or Enter data and press CONTINUE as required. S E T : R U N f t i r  £ y j  « j CLEAR • © Copr. 1949-1998 Hewlett-Packard Co. FLOATING POINT. Any key, other than a digit key, decimal point, CHG SIGN or ENTER EXP, terminates an entry; it is not necessary to clear before entering a new number. CLEAR X sets the X register to 0 and can be used when a mistake has been made in a number entry. Control and Arithmetic Keys ADD, SUBTRACT, MULTIPLY, DIVIDE involve two numbers, so the first number must be moved from X to Y before the second is entered into X. After the two numbers have been entered, the appropriate opera tion can be performed. In the case of a DIVIDE, the dividend is entered into Y and the divisor into X. Then the key is pressed causing the quotient to appear in Y, leaving the divisor in X. One way to transfer a number from the X register to the Y register is to use the double sized key.Q, at the left of the digit keys. This repeats the number in X into Y, leaving X unchanged; the number in Y goes to Z, and the number in Z is lost. Thus, when squaring or cub ing a number, it is only necessary to follow | with or . The key repeats a number in Z to Y leav ing Z unchanged, the number in Y goes to X, and the number in X is lost. The j* key rotates the number in the X and Y registers up and the number in Z down into | rotates the numbers in Z and Y down and the number in X up into Z. Ã- J interchanges the numbers in X and Y. Using the two ROLL keys and , numbers can be placed in any order in the three registers. Functions Available from the Keybord The group of keys at the far left of the keyboard. Fig. 4, gives a good indication of the power of the Model 9 100 A. Most of the common mathematical functions are available directly from the keyboard. Except for ( the function keys operate on the number in X replacing it with the function of that argument. The numbers in Y and Z are left unchanged. .;. :: is located with another group of keys for convenience but operates the same way. The circular functions operate with angles expressed in RADIANS or DEGREES as set by the switch above the keyboard. The sine, cosine, or tangent of an angle is taken with a single keystroke. There are no restric tions on direction, quadrant or number of revolutions of the angle. The inverse functions are obtained by using ¡ 1 key as a prefix. For instance, two key depressions W J ^ ^ K ^ ^ ^ are necessary to obtain the arc sin x: . The angle obtained will be the standard principal value. In radians: - -y < Sin ' x < -y0 < Cos ' x < TT I T ~ , T — ~Y < Tan-1 x < Y The hyperbolic sine, cosine, or tangent is obtained using the Q key as a prefix. The inverse hyberbolic func tions are obtained with three key depressions. Tanh ' x is obtained by Q Q Q . The arc and hyper keys prefix keys below them in their column. Log x and In x obtain the log to the base 10 and the log to the base e respectively. The inverse of the natural log is obtained with the e* key. These keys are useful when raising numbers to odd powers as shown in one of the examples on the pull-out card, Fig. 3. Two keys in this group are very useful in programs. ~l takes the integer part of the number in the X register Fig. function. Keys are in four groups on the keyboard, according to their function. © Copr. 1949-1998 Hewlett-Packard Co. which deletes the part of the number to the right of the decimal point. For example int(— 3.1416) = —3. forces the number in the Y register positive. Storage Registers Sixteen registers, in addition to X, Y, and Z, are avail able for storage. Fourteen of them, 0, 1,2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, can be used to store either one constant or 1 4 program steps per register. The last registers, e and f, are normally used only for constant storage since the program counter will not cycle into them. Special keys located in a block to the left of the digit keys are used to identify the lettered registers. To store a number from the X register the key is used. The parenthesis indicates that another key depres sion, representing the storage register, is necessary to complete the transfer. For example, storing a number from the X register into register 8 requires two key de pressions: . The X register remains unchanged. To store a number from Y register the key is used. The contents of the alpha registers are recalled to X simply by pressing the keys a, b, c, d, e, and f. Recalling a number from a numbered register requires the use of the key to distinguish the recall procedure from digit entry. This key interchanges the number in the Y regis ter with the number in the register indicated by the fol lowing keystroke, alpha or numeric, and is also useful in programs since neither number involved in the trans fer is lost. The CLEAR key sets the X, Y, and Z display registers and the f and e registers to zero. The remaining registers are not affected. The f and e registers are set to zero to initialize them for use with the ï and keys as will be explained. In addition the CLEAR key clears the FLAG and the ARC and HYPER conditions, which often makes it a very useful first step in a program. y=Rsm« x = Rcos* Fig. 5. Variables involved in conversions be tween rectangular and polar coordinates. Coordinate Transformation and Complex Numbers Vectors and complex numbers are easily handled using the keys in the column on the far left of the keyboard. Fig. 5 defines the variables involved. Angles can be either in degrees or radians. To convert from rectangular to polar coordinates, with y in Y and x in X, press Then the display shows 6 in Y and R in X. In converting from polar to rectangular coordinates, d is placed in Y, and R in X, is pressed and the display shows y in Y and x in X. ACC+ and ACC— allow addition or subtraction of vector components in the f and e storage registers. ACC-f adds the contents of the X and Y register to the numbers already stored in f and e respectively; ACC— subtracts them. The RCL key recalls the numbers in the f and e registers to X and Y. Illegal Operations A light to the left of the CRT indicates that an illegal operation has been performed. This can happen either from the keyboard or when running a program. Pressing any key on the keyboard will reset the light. When run ning a program, execution will continue but the light will remain on as the program is completed. The illegal oper ations are: Division by zero. \/x where x < 0 In x where x < 0; log x where x <0 sin ' x where x > 1 ; cos"1 x where x cosh ' x where x < 1 ; tanlr1 x where x|> 1 Accuracy The Model 9100A does all calculations using floating point arithmetic with a twelve digit mantissa and a two digit exponent. The two least significant digits are not displayed and are called guard digits. The algorithms used to perform the operations and generate the functions were chosen to minimize error and to provide an extended range of the argument. Usu ally any inaccuracy will be contained within the two guard digits. In certain cases some inaccuracy will appear in the displayed number. One example is where the func tions change rapidly for small changes in the argument, as in tan x where x is near 90°. A glaring but insignifi cant inaccuracy occurs when an answer is known to be a whole number, but the least significant guard digit is one count low: 2.000000 000 ~ 1.999 999 999. Accuracy is discussed further in the 'Internal Pro gramming' article in this issue. But a simple summary © Copr. 1949-1998 Hewlett-Packard Co. is: the answer resulting from any operation or function will lie within the range of true values produced by a variation of ± 1 count in the tenth digit of the argument. Programming Problems that require many keyboard operations are more easily solved with a program. This is particularly true when the same operations must be performed re peatedly or an iterative technique must be used. A pro gram library supplied with the Model 9100A provides a set of representative programs from many different fields. If a program cannot be found in the library to solve a particular problem, a new program can easily be written since no special experience or prior knowledge of a pro gramming language is necessary. Any key on the keyboard can be remembered by the calculator as a program step except STEP PRGM. This key is used to 'debug' a program rather than as an op eration in a program. Many individual program steps, such as 'sin x' or 'to polar' are comparatively powerful, and avoid the need of sub-routines for these functions and the programming space such sub-routines require. Registers 0, 1,2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d can store 14 program steps each. Steps within the registers are numbered 0 through d just as the registers themselves are numbered. Programs can start at any of the 196 pos sible addresses. However 0-0 is usually used for the first step. Address d-d is then the last available, after which the program counter cycles back to 0-0. Registers f and e are normally used for storage of con stants only, one constant in each register. As more con stant storage is required, it is recommended that regis ters d, then c, then b, etc., are used starting from the bottom of the list. Lettered registers are used first, for the frequently recalled constants, because constants stored in them are more easily recalled. A register can be used to store one constant or 14 program steps, but not both. Branching The bank on the far right of the keyboard, Fig. 4, con tains program oriented keys. is used to set the pro gram counter. The two sets of parentheses indicate that this key should be followed by two more key depressions indicating the address of the program step desired. As a program step, 'GO TO' is an unconditional branch in struction, which causes the program to branch to the address given by the next two program steps. The 'IF' keys in this group are conditional branch instructions. With . and the numbers contained in the X and Y registers are compared. The indicated condition is Fig. 6. Flow chan of a program to compute N! (top). Each step is shown (bottom) and the display lor each regis ter. A new value for N can be entered at the end of the program, since END automatically sets the program counter back to 0-0. tested and, if met, the next two program steps are ex ecuted. If the first is alphameric, the second must be also, and the two steps are interpreted as a branching address. When the condition is not met, the next two steps are skipped and the program continues. | is also a very useful conditional branching instruction which tests a 'yes' or 'no' condition internally stored in the calculator. This condition is set to 'yes' with the SET FLAG from the keyboard when the calculator is in the display mode or from a program as a program step. The flag is set to a 'no' condition by either asking IF FLAG in a program © Copr. 1949-1998 Hewlett-Packard Co. or by a CLEAR instruction from the keyboard or from a program. S.33GBH5BI5 Z75 S . d Data Input and Output 3 E Fig. 7. Program step address and code are displayed in the X register as steps are entered. After a program has been entered, each step can be checked using the STEP PRGM key. In this display, step 2-d is 36, the code for multiply. Fig. 8. Programs can be entered into the calculator by means of the magnetic program card. The card is in serted into the slot and the ENTER button pressed. Data can be entered for use in a program when the machine is in the display mode. (The screen is blank while a program is running.) A program can be stopped in several ways. The key will halt the machine at any time. The operation being performed will be completed before returning to the display mode. As a program step, STOP stops the program so that answers can be dis played or new data entered. END must be the last step in a program listing to signal the magnetic card reader; when encountered as a program step it stops the ma chine and also sets the program counter to 0-0. As a program step, PAUSE causes a brief display dur ing program execution. Nine cycles of the power line frequency are counted — the duration of the pause will be about 150 ms for a 60 Hz power line or 180 ms for a 50 Hz power line. More pauses can be used in sequence if a longer display is desired. While a program is running the PAUSE key can be held down to stop the machine when it comes to the next PAUSE in the program. PAUSE provides a particularly useful way for the user and the machine to interact. It might, for instance, be used in a program so that the convergence to a desired result can be observed. Other means of input and output involve peripheral devices such as an X-Y Plotter or a Printer. The PRINT key activates the printer, causing it to print information from the display register. As a program step, PRINT will interrupt the program long enough for the data to be accepted by the printer and then the program will continue. If no printer is attached, PRINT as a program step will act as a STOP. The FMT key, followed by any other keystroke, provides up to 62 unique commands to peripheral equipment. This flexibility allows the Model 9100A to be used as a controller in small systems. Sample Program — N! A simple program to calculate N! demonstrates how the Model 9100A is programmed. Fig. 6 (top) shows a flow chart to compute N! and Fig. 6 (bottom) shows the program steps. With this program, 60! takes less than l/t second to compute. Fig. 9. Magnetic programming card can record two 196step programs. To prevent accidental recording of a new program over one to be saved, the corner of the card is cut as shown. Program Entry and Execution After a program is written it can be entered into the Model 9100A from the keyboard. The program counter is set to the address of the first program step by using the © Copr. 1949-1998 Hewlett-Packard Co. GO TO () () key. The RUN-PROGRAM switch is then switched from RUN to PROGRAM and the program steps entered in sequence by pushing the proper keys. As each step is entered the X register displays the address and key code, as shown in Fig. 7. The keys and their codes are listed at the bottom of the pull-out card, Fig. 3. Once a program has been entered, the steps can be checked using the STEP PRGM key in the PROGRAM mode as explained in Fig. 7. If an error is made in a step, it can be corrected by using the . key without having to re-enter the rest of the program. To run a program, the program counter must be set to the address of the first step. If the program starts at 0-0 the keys are depressed, or simply just since this key automatically sets the program counter to 0-0. CONTINUE will start program execution. Richard E. Monnier Dick Monnier has a BSEE from the University of California at Berkeley, 1958, and an MSEE from Stanford University, 1961. Dick has been with HP since 1958 when he joined the group working on sampling oscilloscopes. He has been project leader on the Models 120B, 132Aand 140A oscilloscopes and the Model 191A television waveform monitor prior to the transfer of the project to HP's Colorado Springs Division. Since early 1966 he has been Section Leader responsible for the 91 OOA Calculator project in Palo Alto. Dick holds several patents and is a Member of IEEE. Magnetic Card Reader-Recorder One of the most convenient features of the Model 9100A is the magnetic card reader-recorder, Fig. 8. A program stored in the Model 9 1 OOA can be recorded on a magnetic card, Fig. 9, about the size of a credit card. Later when the program is needed again, it can be quickly re-entered using the previously recorded card. Cards are easily duplicated so that programs of common interest can be distributed. As mentioned earlier, the END statement is a signal to the reader to stop reading recorded information from the card into the calculator. For this reason END should not be used in the middle of a program. Since most pro grams start at location 0-0 the reader automatically ini tializes the program counter to 0-0 after a card is read. SPECIFICATIONS integer part of a number, and entering the value of Keys are also available for positioning and storage operations. HP Model 91 OOA The HP Model 9100A Is a programmable, electronic calcu lator which performs operations commonly encountered in scientilic and engineering problems. Its log, trig and ma ematical functions are each performed with a single ey stroke, providing fast, convenient solutions to intricate eg ations. Computer-like memory enables the calculator to 8 re instructions and constants for repetitive or iterative s utions. The easily-readable cathode ray tube Instantly disp entries, answers and intermediate results. OPERATIONS DIRECT KEYBOARD OPERATIONS INCLUDE: ARITHMETIC: addition, subtraction, multiplication, division and square-root. LOGARITHMIC: log X. In X and e'. TRIGONOMETRIC: sin x, cos x. tan x, sin-!x, cos- x and tan x (x in degrees or radians). HYPERBOLIC: sinh x. cosh x. tanh x. sinh x. cosh x, and tanh-'x. COORDINATE TRANSFORMATION: polar-to-rectangular. rectangular-to-polar. cumulative addition and sub traction of vectors. MISCELLANEOUS: other single-key operations include — taking the absolute value of a number, extracting the The magnetic card reader makes it possible to handle most programs too long to be held in memory at one time. The first entry of steps can calculate intermediate results which are stored in preparation for the next part of the program. Since the reader stops reading at the END state ment these stored intermediate results are not disturbed when the next set of program steps is entered. The stored results are then retrieved and the program continued. Linking of programs is made more convenient if each part can execute an END when it finishes to set the pro gram counter to 0-0. It is then only necessary to press CONTINUE after each entry of program steps. S PROGRAMMING These times include core access of 16 microseconds. GENERAL WEIGHT: Net 40 Ibs. (18,1 kg.); shipping 65 Ibs. {29.5 kg.). POWER: 115 or 230 V ±10%. 50 to 60 Hz. 400 Hz. 70 watts. DIMENSIONS: 8'/4" high, 16" wide. 19" deep. Trie program mode allows entry of program instructions, via the keyboard. Into program memory. Programming con sists of pressing keys in the proper sequence, and any key on the keyboard is available as a program step. Program capacity is 196 steps. No language or code-conversions are required A sell-contained magnetic card reader/recorder records programs from program memory onto wallet-size magnetic cards for storage. It also reads programs from cards into program memory for repetitive use. Two programs of 196 steps each may be recorded on each reusable card. Cards may be cascaded for longer programs. ACCESSORIES FURNISHED AT NO CHARGE: 09100-90001 Operating and Programming manual, $5.00. 09100-90002 Program library binder containing sample programs. S30 00 5060-5919 Box of 10 magnetic program cards. $10.00. 09100-90003 Pad of 100 program sheets. $2.50. 09100-90004 Magnetic card with pre-recorded diagnostic program. $2.50. 9320-1157 Pull-out Instruction card mounted In calculator. $5.00. 4040-0350 Plastic dust cover. $2.50. SPEED ADDITIONAL ACCESSORIES AVAILABLE: 5000-5884 Single magnetic card, $2.00 09100-90000 Box of 5 program pads. $10.00. Average times for total performance of typical operations, including decimal-point placement: add. subtract: 2 milliseconds multiply: 12 milliseconds divide: 18 milliseconds square-root: 19 milliseconds sin. cos. tan: 280 milliseconds In x: 50 milliseconds e-: 110 milliseconds © Copr. 1949-1998 Hewlett-Packard Co. PRICE: HP Model 9100A, $4900.00. PERIPHERALS: Printer. X-Y plotter and input/output inter face will be available soon. MANUFACTURING DIVISION: LOVELAND DIVISION P.O. Box 301 815 Fourteenth Street N.W. Loveland, Colorado 80537 Hard-Wired Logic Gates (Instructions) Fig. a conventional, processing unit block diagram. This system is a marriage of conventional, reli able and logic to a 32,000-bit read-only memory and a coincident current core memory. Hardware Design of the Model 9100A Calculator By Thomas E. Osborne Al.L KEYBOARD FUNCTIONS IN THE MODEL 9100A are implemented by the arithmetic processing unit, Figs. 1 and 2. The arithmetic unit operates in discrete time peri ods called clock cycles. All operations are synchronized by the clock shown at the top center of Fig. 1 . The clock is connected to the control read only mem ory (ROM) which coordinates the operation of the pro gram read only memory and the coincident current core read/write memory. The former contains information for implementing all of the keyboard operations while the latter stores user data and user programs. All internal operations are performed in a digit by digit serial basis using binary coded decimal digits. An addition, for example, requires that the least significant digits of the addend and augend be extracted from core, then added and their sum replaced in core. This process is repeated one BCD digit at a time until the most sig nificant digits have been processed. There is also a sub stantial amount of 'housekeeping' to be performed such as aligning decimal points, assigning the proper algebraic sign, and floating point normalization. Although the im plementation of a keyboard function may involve thou sands of clock cycles, the total elapsed time is in the millisecond region because each clock cycle is only 825 ns long. The program ROM contains 512 64-bit words. When the program ROM is activated, signals (micro-instruc tions) corresponding to the bit pattern in the word are sent to the hard wired logic gates shown at the bottom of Fig. I . The logic gates define the changes to occur in the flip flops at the end of a clock cycle. Some of the micro-instructions act upon the data flip flops while others change the address registers associated with the program ROM. control ROM and coincident current core mem ory. During the next clock cycle the control ROM may ask for a new set of micro-instructions from the program ROM or ask to be read from or written into the coinci dent current core memory. The control ROM also has 10 © Copr. 1949-1998 Hewlett-Packard Co. the ability to modify its own address register and to issue micro-instructions to the hard wired logic gates. This flexibility allows the control logic ROM to execute spe cial programs such as the subroutine for unpacking the stored constants required by the keyboard transcendental functions. Control Logic The control logic uses a wire braid toroidal core read only memory containing 64 29-bit words. Magnetic logic of this type is extremely reliable and pleasingly compact. The crystal controlled clock source initiates a current pulse having a trapezoidal waveform which is directed through one of 64 word lines. Bit patterns are generated by passing or threading selected toroids with the word lines. Each toroid that is threaded acts as a transformer to turn on a transistor connected to the output winding of the toroid. The signals from these transistors operate the program ROM, coincident current core, and selected micro-instructions. Coincident Current Core Read/Write Memory The 2208 (6 x 16 x 23) bit coincident current memory uses wide temperature range lithium cores. In addition, the X, Y, and inhibit drivers have temperature compen sated current drive sources to make the core memory insensitive to temperature and power supply variations. The arithmetic processing unit includes special cir cuitry to guarantee that information is not lost from the core memory when power is turned off and on. Fig. 3. Displayed characters are generated by modulating these figures. The digit 1 is shifted to the center of the pattern. a low transmissivity filter in front of the CRT. Ambient light that usually tends to 'wash out' an image is at tenuated twice by the filter, while the screen image is only attenuated once. All the displayed characters are 'pieces of eight! Six teen different symbols are obtained by intensity modu lating a figure 8 pattern as shown in Fig. 3. Floating point numbers are partitioned into groups of three digits and the numeral 1 is shifted to improve readability. Zeros to the left of the most significant digit and insignificant zeros to the right of the decimal point are blanked to avoid a confusing display. Fixed point numbers are auto matically rounded up according to the decimal wheel setting. A fixed point display will automatically revert to floating point notation if the number is too large to be displayed on the CRT in fixed point. Multilayer Instruction Logic Board All of the hard wired logic gates are synthesized on Power Supplies The arithmetic processing unit operates from a sin gle — 15 volt supply. Even though the power supply is highly regulated, all circuits are designed to operate over a voltage range of —13.5 to -16.5 volts. Display The display is generated on an HP electrostatic cath ode ray tube only 1 1 inches long. The flat rectangular face place measures 31Ã" x 4i:!ir, inches. The tube was specifically designed to gen erate a bright image. High contrast is obtained by using Fig. 2. Arithmetic unit assembly removed from the calculator. 11 © Copr. 1949-1998 Hewlett-Packard Co. the instruction logic board using time-proven diode-re sistor logic. The diodes and resistors are located in sep arate rows, Fig. 4 All diodes are oriented in the same direction and all resistors are the same value. The maze of interconnections normally associated with the back plane wiring of a computer are located on the six inter nal layers of the multilayer instruction logic board. Sol der bridges and accidental Fig. are, at circuit boards which make up the arithmetic unit are, left to right at shorts caused by test probes top, core board, control logic, flip-flop, core and drivers, core sense amplifiers and inhibit, flip-flop, and side board. Large board at the lower left is the multilayer instruc shorting to leads beneath tion board and the program ROM is at the right. The magnetic card reader and its components are all but elimi associated circuitry is at the bottom. nated by not having intercon nections on the two outside surfaces of this multilayer board. The instruction logic bination sense amplifier, gated-latch circuits are located board also serves as a motherboard for the control on each side of the ROM data board. The outputs of logic board, the two coincident core boards and the two these circuits control the hard wired logic gates on the flip flop boards, the magnetic card reader, and the key instruction logic board. board, it also contains a connector, available at the rear Side Boards of the calculator, for connecting peripherals. The program ROM printed circuit board and the in struction logic board are interconnected by the side Flip Flops boards, where preliminary signal processing occurs. The Model 91 OOA contains 40 identical J-K flip flops, each having a threshold noise immunity of 2.5 volts. Worst case design techniques guarantee that the flip flops will operate at 3 MHz even though 1.2 MHz is the max imum operating rate. The Keyboard The keyboard contains 63 molded plastic keys. Their markings will not wear off because the lettering is im bedded into the key body using a double shot injection molding process. The key and switch assembly was spe cifically designed to obtain a pleasing feel and the proper amount of tactile and aural feedback. Each key oper ates a single switch having gold alloy contacts. A con tact closure activates a matrix which encodes signals on six data lines and generates an initiating signal. This sig nal is delayed to avoid the effects of contact bounce. An electrical interlock prevents errors caused by pressing more than one key at a time. Program Read Only Memory The 32,768 bit read only program memory consists of 5 1 2 64-bit words. These words contain all of the oper ating subroutines, stored constants, character encoders, and CRT modulating patterns. The 512 words are con tained in a 16 layer printed-circuit board having drive and sense lines orthogonally located. A drive line con sists of a reference line and a data line. Drive pulses are inductively coupled from both the reference line and data line into the sense lines. Signals from the data line either aid or cancel signals from the reference line pro ducing either a 1 or 0 on the output sense lines. The drive and sense lines are arranged to achieve a bit density in the ROM data board of 1000 bits per square inch. The program ROM decoder/driver circuits are located directly above the ROM data board. Thirty-two corn- Magnetic Card Reader Two complete 196 step programs can be recorded on the credit card size magnetic program card. The record ing process erases any previous information so that a card may be used over and over again. A program may be protected against accidental erasure by clipping off the corner of the card. Fig. 9, page 8. The missing cor12 © Copr. 1949-1998 Hewlett-Packard Co. The case covers are die cast aluminum which offers durability, effective RFI shielding, excellent heat trans fer characteristics, and convenient mechanical mounts. Removing four screws allows the case to be opened and locked into position. Fig. 5. This procedure exposes all important diagnostic test points and adjustments. The keyboard and arithmetic processing unit may be freed by removing four and seven screws respectively. Any component failures can be isolated by using a di agnostic routine or a special tester. The faulty assembly is then replaced and is sent to a service center for com puter assisted diagnosis and repair. Reliability Extensive precautions have been taken to insure maxi mum reliability. Initially, wide electrical operating mar gins were obtained by using 'worst case' design tech niques. In production all transistors are aged at 80% of rated power for 96 hours and tested before being used in the Model 9100A. Subassemblies are computer tested and actual operating margins are monitored to detect trends that could lead to failures. These data are ana lyzed and corrective action is initiated to reverse the trend. In addition, each calculator is operated in an en vironmental chamber at 55 °C for 5 days prior to ship ment to the customer. Precautions such as these allow Hewl