US3432830A

US3432830A - Transformer read-only storage construction

Info

Publication number: US3432830A
Application number: US412665A
Authority: US
Inventors: Charles E Owen; Daniel M Taub; William A Warwick
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1964-11-20
Filing date: 1964-11-20
Publication date: 1969-03-11
Anticipated expiration: 1986-03-11

Description

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet of 12 FIG. 1

12c 12D |2E 12F 9c 90 9E 9F INVENTORS CHARLES E. OWEN ANTONY PROUDMAN DANIEL M TAUB WILLIAM A. WARWICK I CwiCKb-n ATTORNEY l March 11, 1969 c. E. OWEN ETAL TRANSFORMER'READONLY STORAGE CONSTRUCTION Sheet g of 12 Fild Nov. 20, 1964 FIG. 3

March 11 1 969 O c. E. OV\A/EN ETAL TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20 1964 Sheet 3 of 12 FIG. 7

M p 550mm Jmufim p Q m UUUUU U MW D nmmuflmmmmzm Mil I M 3 i C. E. OWEN ETAL March 11, 1969 TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet 4 of 12 FIG. 8

E. w Q Ufi/ v V 0 U U H o Q U U Tll l H w fi U? M a y 5 FIG. 9

March 11, 1969 Filed NOV. 20, 1964 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Sheet 6' of 12 FIG. 10

FIG. 11

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet 6 of 12 FIG. 20 /2 [/N 1 W t /2 Q FIG. 21

FIG. 13

C. E. OWEN ETAL TRANSFORMER READ-ONLY STORAGE CONSTRUCTION March 1 1, 1969 Filed Nov. 20, 1964 Sheet FIG. 15

March 11, 1969 c, OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet 8 of 12 FIG. 16

FPL PL RL RL /NPU7 CURRENT f T/ME OUTPUT CURRENT HB/NARY V) A T/ME OUTPUT CURRENT (BM/AR) o) A A A v r/ME FIG. 17

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 sheet 9 of 12 FIG. 18

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet /0 of 12 FIG. 22

A78 KI] LZZZ'IIIII- FIG. 23

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed NOV. 20, 1964 Sheet of 12 FIG. 24 43 49 mtlmd FIG. 43 49 42 I Mai-Ch 11, 1969 5. OWEN ETAL TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet 5 of 12 FIG. 27

vvvvvvvvvvgvvv United States Patent O 3,432,830 TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Charles E. Owen, Eastleigh, Antony Proudman, Awbridge, near Romsey, Daniel M. Taub, Winchester, and William A. Warwick, South Wonston, near Winchester, England, assignors to International Business Machines Corporation,'Armonk, N.Y., a corporation of New York Filed Nov. 20, 1964, Ser. No. 412,665 U.S. Cl. 340-174 5 Claims Int. Cl. Gllb 5/00 ABSTRACT OF THE DISCLOSURE An improved read-only memory is disclosed of the type in which each bit position of the memory has a transformer core that couples a large number of primary windings to a single secondary winding. The primary windings are interconnected to form words of the memory and selecting a particular word produces a pattern of signals on the secondary windings. The primary windings for each word are formed on a longitudinal tape that has apertures for receiving the legs of the transformers at each bit position. A structure is disclosed that reduces the ringing that can occur in a device of this type. The longitudinal conductors in adjacent tapes are staggered so as to reduce capacitive coupling between the longitudinal conductors. Each transformer core is fitted with a closed loop having an appropriate resistance to damp the ringmg.

between such longitudinal conductors, thus reducing the' ringing. It also includes a technique for damping oscillations by fitting each transformer core with a closed loop of resistance conductor.

ENVIRONMENT OF THE INVENTION The invention operates with a transformer read-only storage device such as described in the following publication:

D. M. Taub and B. W. Kington, The Design of Transformer (Dimond Ring) Read-Only Stores, IBM Journal of Research and Development, vol. 8, No. 4, September 1964, pp. 443-459.

Such a transformer read-only store includes a group of U-shaped cores mounted in a row and equipped with I-shaped keepers that close the inductive loop. The I- shaped keepers each are equipped with a secondary winding which connects to sense amplifiers for output. The U-shaped cores are inserted through slots in each of a group of flexible tapes which carry the primary winding conductors. The flexible tapes are suitably punched so that the primary conductors selectively pass inside the particular core or outside the particular core to give

output values

1 and 0 respectively. There may be, for example, sixty-four primary conductor tapes for a group of sixty cores. That is, the cores might be equipped to produce sixty-four words of information, each word having sixty bits.

When the word associated with a given conductor tape is selected and driven, normal transformer action provides outputs on the secondary windings. If the primary conductor passes inside the core, transformer action provides an output on the secondary conductor. If the conductor on the second core does not pass through the core but rather passes outside it, the flux coupling is such that the transformer action does not occur and there is no output on the secondary conductor. The output condition is given the 1 value; the no-output condition is given the 0 value.

Because of the great inductances and capacitances involved, the transformer read-only storage device is subject to ringing oscillations, which can be aggravated by certain types of data arrangements.

CHARACTERISTICS OF THE INVENTION The invention is a technique for minimizing oscillatory noise transients in a transformer read-only memory, by controlling the production of noise on the input tapes and by dissipating noise actually produced in a winding about the cores themselves.

OBJECTS The object of the present invention is to provide an improved transformer read-only memory by reducing ringing oscillations.

Another object of the invention is to reduce capacitive coupling between adjacent input tapes of a transformer read-only storage.

Another object of the invention is to dissipate noise transients developed by an individual transformer in a transformer read-only storage.

FEATURES A feature of the invention is the selective offsetting of adjacent input tapes of a transformer read-only storage to minimize capacitive coupling between drive windings on adjacent tapes.

Another feature of the invention is the provision of a shorted turn of resistance conductive material about each core of a transformer read-only storage device so as to dissipate noise transients within the conductive loop.

ADVANTAGES An advantage of the invention is the provision to a transformer read-only storage device of a more noisefree signal.

SUMMARY OF THE INVENTION The invention relates to construction features for reducing ringing oscillations in a read-only storage device of the transformer type. A transformer read-only storage device is particularly subject to ringing because of the large inductances of the transformer cores 10 and the large capacitances of the input conductors 11 which are carried on closely spaced plastic tapes 7 and selectively punched for data content.

Oscillations are minimized by staggering the placement of

conductors

11A, 11B and 11C respectively on

tapes

7A, 7B and 70. Corresponding conductors on adjacent tapes are thus kept at a distance considerably greater than the thickness of the tapes, greatly decreasing their mutual capacitance.

An auxiliary tape 8 is included to provide damping of the individual cores. Areas of resistive material 9 are arranged in closed loops about the holes in tape 8 through which the core legs are to pass. The resistance of each loop 9 is -a R /n where:

a is the number of loops linking one transformer core n is the number of transformers R is the resistance value required to provide critical damping to the inductance and capacitance present.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 illustrates a transformer read-only storage device according to the invention;

FIGURE 2 shows a number of transformer cores connected to store a data word according to the invention;

FIGURE 3 shows the structure of a transformer core and a method of storing data words on a tape according to the invention;

FIGURES 4 and 5 indicate the effect of plating the transformer cores with copper according to the invention;

FIGURE 6 shows a stack of tapes arranged for use in the T.R.O.S. according to the invention;

FIGURE 7 shows a complete tape for use in T.R.O.S. prior to programming;

FIGURE 8 shows one method by which the tape may be programmed to store data words;

FIGURE 9 shows another method by which the tape may be programmed to store data words;

FIGURE 10 shows an improved tape for use in the T.R.O.S. according to the invention;

FIGURES 11 and 12 show one method of connecting a tape to drive and select circuitry;

FIGURE 13 shows another method of connecting a tape to drive and select circuitry;

FIGURE 14 shows the preferred method of stacking tapes in T.R.O.S. according to the invention;

FIGURE 15 is a side elevation of FIGURE 14 in the direction of the arrow A;

FIGURE 16 shows a schematic representation of a portion of the T.R.O.S. with a pattern of stored information which aggravates oscillations;

FIGURE 17 shows output pulses received in response to an input pulse for the two values of information stored;

FIGURE 18 represents the equivalent circuit of FIG- URE 16;

FIGURE 19 is another form of the equivalent circuit shown in FIGURE 18;

FIGURE 20 is a simplified form of FIGURE 19;

FIGURE 21 is a simplified form of FIGURE 20;

FIGURE 22 shows a portion of a resistive tape used to damp oscillations in the T.R.O.S. according to the invention;

FIGURE 23 shows how oscillations are eliminated by serially damping the transformer cores used according to the invention;

FIGURES 24, 25, and 26 show various staggers of primary windings used in T.R.O.S. to reduce inter-primary capacitive coupling according to the invention;

FIGURE 27 shows an exploded view of the T.R.O.S. module according to the invention;

GENERAL DESCRIPTION FIGURE 1 illustrates a read-only storage device constructed according to the invention. Transformer core 10 is equipped with an output conductor 12 (secondary winding) and several data tapes 7. The data tapes include ladder configuration conductors 11 which are selectively punched to direct electrical currents selectively through or not through the cores for 1 and 0 values.

Data tapes

7A, 7B and 7C are nonidentical in that the

ladder configuration conductors

11A, 11B and 11C which they carry are laterally offset. This staggering of conductors provides sufiicient dielectric spacing between conductors on adjacent tapes to reduce capacitance and thus reduce ringing.

A fourth type of tape, tape '8, contains areas 9 of conductive material arranged to form resistive loops about the cores 10. The resistances of these loops are calculated to provide critical damping to the cores.

A binary bit of information is represented in the transformer read-only store (T.R.O.S.) by the presence or absence of a primary winding on a current transformer.

This is illustrated in FIGURE 2 which shows several transformer cores 10A-10F, a primary winding 11 and several secondary windings 12A12F. Primary winding 11 bypasses the

cores

10C, 10D and 10F; therefore a current pulse on the primary winding 11 produces no out put on their secondary windings 12C, 12D, 12F. This represents binary 0 bits of information. Primary winding 11 threads through

cores

10A, 10B and 10E and so a current pulse on the winding 11 will produce an output signal on their secondary windings 12A,.12B and 12E. This represents binary 1 bits of information. A data word is made up of a number of these transformers having a common primary winding 11 which threads, or does not thread, through the cores 10 depending on the binary bits of information required to make up the data word. FIGURE 2 shows six transformers wired to store the data word 1 10 010.

SPECIFIC DESCRIPTION In practice, it has been found convenient to manufacture the transformer cores in two parts. This makes the assembly of the transformer read-only store much simpler as will be seen from the following description. A transformer core is shown in FIGURE 3 and is seen to consist of a U-shaped part 13 and an I-shaped part 14. The Iasha-ped part 14 is used to close the open end of the U-shaped part 13 and so produce a transformer core which is rectangular in shape. The figure also shows a flexible insulating carrier 15 having two rows of

apertures

16 and 17 punched along its length. The two limbs of the U-shaped part 13 of a core are shown threaded through two of these apertures, one in row 16 and the other in the corresponding aperture in row 17. Although, for the sake of clarity, only one transformer core is shown in position, it will be understood that the portion of the carrier 15 shown in the figure has

sufficient apertures

16 and 17 to accommodate siX such cores.

The primary winding is deposited, or otherwise formed as a thin conductive strip 18 on the surface of the carrier 15 so that it by-passes or threads through the assembled cores depending upon the information to be stored. It is now evident why it is convenient to manufacture the core in two parts. The open end of the U-shaped part 13 is closed with the I-shaped part 14 which carries a sense winding 19 which is, in fact, the secondary winding of the transformer.

Since both limbs of the Uashaped part 13 of each core in the assembly pass through apertures in the carrier 15, a further primary winding is provided which threads or by-passes the cores to store a second data word. This further primary winding is also deposited as a thin conductive strip 21 on the surface of the carrier 15.

Two data words have thus been stored on the carrier 15 using the same transformer cores for both. Read out is accomplished by applying a current pulse to one or the other of the

strips

18 or 20 whereupon the data word stored by the selected strip is produced as a parallel combination of signals and no-signals on the sense windings 19 of the cores.

Before continuing with the description of the construction of the transformer read-only store, the final form of the transformer cores to be used will be discussed in detail.

The U-shaped parts 13 and I-shaped parts 14 which form the magnetic paths of the current transformers consist of a saft ferrite material (as distinct from square loop ferrite material) and are coated with a thin layer of copper plating. This layer of copper is provided to reduce the leakage flux associated with the primary and secondary windings. The plating permits flux which is parallel to its plane to enter the ferrite, but flux which is perpendicular to it to be cancelled. The effect can be best understood by reference to FIGURES 4 and 5.

In FIGURE 4 a magnetic fiux B having a magnetizing force H is shown perpendicular to a copper sheet 22. If

the copper is assumed to be a perfect conductor, then eddy currents in the copper produce an equal and opposite magnetic force to H such that B is cancelled. A perpendicular component of magnetic flux (leakage flux) will not, therefore, pass through a perfectly conducting sheet of metal.

The conducting sheet 22 has no effect on a parallel component of flux B as shown in FIGURE 5.

This principle of screening is applied to the transformer cores by plating them with copper. The flux enters the ferrite quite easily, but after entering, if it tries to take a shorter reluctance path, say across the window of the core, then its perpendicular component is cancelled. The flux in the ferrite can, therefore, only follow a path outlined by the copper and so, theoretically, no leakage flux can exist between any two windings on the core.

In practice, however, the plating has to be provided with a gap 23 which extends around the U-shaped part 13 of each core to prevent the copper plating acting as a shortcircuited turn. Some leakage of flux can occur at the gapping positions. The gap 23 can be made on the edge of the cores, 'but the most favored position is in the center of the face as shown in FIGURE 3. The face of the I-shaped part 14 which makes contact with the open end of the U- shaped part is left unplated and so no gap is required on the member.

The gap 23 in the copper can be made by one of several techniques; for example, sawing (ultrasonic or mechanical) and grinding. Whichever method is used, care has to be taken that the cut does not become contaminated with low resistivity foreign matter.

Two soft ferrite materials from which the transformer cores can be made are manganese zinc ferrite and nickel zinc ferrite. Cores made from manganese zinc ferrite must be coated with a layer of an insulating material to prevent the copper layer from making contact with the ferrite. This is because manganese zinc ferrite has a high per mittivity and low resistivity and if the copper made contact with this material, it would act as a single turn secondary winding with the ferrite, that is, as a very low series resistance. A suitable insulating material is araldite which has the additional advantage of being a strong adhesive. The coating with araldite is not necessary for cores made of nickel zinc ferrite. After plating the cores are covered with a protective coating which helps to prevent peeling and corrosion of the plating and also improves the appearance of the cores.

A plurality of flexible carriers 15 or tapes, as they will hereinafter be called, are then taken, each identically punched with rows of

apertures

16 and 17, and are superimposed one upon the other so that the rows of apertures are in alignment. The limbs of the U-shaped parts 13 of the transformer cores are then passed through corresponding apertures in all of the plurality of tapes 15 as shown in FIGURE 6. Each tape 15 has two primary windings in the form of

conductive strips

18 and 21 which store two data words on each tape as has already been explained. The number of tapes 15 superimposed one on the other is limited only 'by the size of the transformer core and in the preferred embodiment of this invention, one hundred and twenty-eight such tapes are used. The number of transformers required is determined by the number of bits required to make the data word. A word of sixty bit length has been found sufficient and so each

row

16 and 17 contains sixty apertures to receive sixty U-shaped parts 13 of the cores. Thus with one hundred and twentyeight tapes arranged in a stack and threaded by sixty transformers, a storage capacity of two hundred and fifty-six words of sixty bit length is obtained. Information is read out by passing a drive current along one or other of the

conductive strips

18 or 21 on a selected tape 15 and the selected word is received as a parallel combination of signals and no-signals on the sixty sense windings 19 wound on the I-shaped part 14 of the cores.

It would be an arduous task if the

conductive strips

18 and 21 had to be separately deposited on each tape 15 to thread through or by-pass the cores according to the information words to be stored. This difficulty is overcome in the manner described below with reference to FIG- URE 7.

Onto each tape 15, which has been identically punched with two rows of

apertures

16 and 17, are deposited two

identical ladder networks

24 and 25. These ladder networks are of such dimensions and so positioned on the tape that each aperture in the row of apertures 16 is symmetrically positioned between separate rungs of the ladder network 24 and each aperture in the row of apertures 17 is symmetrically positioned between separate rungs of the ladder network 25. It only remains now to remove the parts of the ladder networks on the inside or outside of each aperture so that two continuous conductors are formed from one end of the tape 15 to the other that thread or by-pass the transformer cores, depending on the two data words to be stored on each tape 15. In order to show the ladder network to best advantage, only one transformer core 13 is shown in position in FIGURE 7.

Each tape 15 is also provided with an extension 26 at one end and an extension 27 at the other end. Connecting leads 28 and 29 are deposited onto the extensions 26 to connect the ends of the

ladder networks

24 and 25 to tags 31 and 32 provided at the end of the extension. Similarly, connecting leads 33 and 34 are deposited onto the extension 27 to connect the other ends of the

ladder networks

24 and 25 to

tags

35 and 36 provided at the end of that extension. In use, the

tags

31, 32, 35 and 36 are connected to input and output circuitry for selection and read-out of a particular data word stored.

Finally, each tape 15 is provided with a row of sprocket holes 37 arranged symmetrically along the length of the tape between the rows of

apertures

16 and 17. One sprocket hole is provided between the corresponding aperture in the

rows

16 and 17 so that the tape 15 can be advanced in a machine step by step for removing unwanted portions of the

ladder networks

24 and 25.

The removing of portions of the

ladder networks

24 and 25 to form the two continuous conductive strips from one end of the tape to the other and to give the required data words is known as programming. Tape programming can be carried out in a number of ways. The unwanted portions of the ladder networks may be punched out. For example, to store a binary 1 bit of information in a particular transformer core the side of the ladder network passing outside the limb of that core must be broken. A current pulse applied to the programmed ladder network will then pass through the core and an output representing a binary 1 bit will be received on the sense winding of that core.

A portion of the tape 15 which has been programmed by punching is shown in FIGURE 8. The punch used in this instance is triangular in shape and of such a dimension that the apex of the punch hole 38 extends a sufficient distance to break the side of the ladder network which is unwanted. The tape is fed through a conventional punching machine step 'by step and one or the other side of the two

ladder networks

24 and 25 is punched out.

The shape of the punch hole 38 is immaterial, providing it cuts through the unwanted part of the networks. Only one transformer core has been shown in position in this figure and the binary bits of information stored by the punching are indicated. For example, a current pulse applied to the left hand side of the programmed ladder network 24 of the tape 15 shown in FIGURE 8 will pass through the first and second cores (binary 1 'bits), by-pass the third and fourth cores (binary 0 bits), pass through the fifth (binary 1 bit) and by-pass the sixth core (binary 0 bit). Thus the data word 1 1 0 0 1 0 will be received on the six sense windings wound around the I-shaped parts of the six transformer cores of the 7 tape. Similarly, the data word 1 0 1 1 0 is stored by the programmed ladder network 25 of the tape.

Another method of programming the tape is by etching. This is particularly useful when a large quantity of tapes are required all of which contain the same information. The method used in this case is known as a photoresistive etch process. In this method a number of copies is made of the master negative of the unprogrammed tape. Each of the negatives is then altered by blanking out the appropriate positions on the two ladder networks for binary 1 bits or binary 0- bits to form a programmed negative. A normal photo-resistive etch is then carried out on the tape which is first completely coppered on one surface. A tape programmed by this etching technique is shown in FIGURE 9.

Finally, the tape can be programmed by directing a fine abrasive, pumped by air pressure through a nozzle, onto the unwanted portions of the ladder networks. The programmed tape would also look like that shown in FIGURE 9.

The read only store so far described consists of a number of tapes each storing two words of sixty bit length. Because of the construction of the tape, connections have to be made at each end of every tape in order to select and read out a particular data word. Another point which may be considered as a disadvantage is that the length of each tape 15 is determined by the number of bits in each word to be stored on the tape. In this case (a word length of sixty bits) the tape would have to be long enough to accommodate sixty transformers in a line. Both these drawbacks have been overcome by designing a tape as shown in FIGURE 10.

This tape, labelled 39, is so designed that it still stores two data words each of sixty bits and yet its length is reduced by approximately half with only a small increase in width. Connections for selecting and reading out a word are only required at one end.

In this arrangement, the transformer cores are provided in two parallel rows along the tape and half of each data word is stored in one row and the other half in the other row. As in the previous case, each tape 39 is identical before the programming operation. Each tape 39 is provided with four rows of

apertures

41, 42, 43 and 44 to accommodate the limbs of the U-shaped parts 13 of the two rows of transformer cores. Each row of apertures is provided with an enclosing ladder network as before. The ladder networks for the rows of

apertures

41, 42, 43 and 44 have been labelled 45, 46, 47 and 48 respectively. A row of sprocket holes 49 extend along the length of the tape having two rows of apertures symmetrically positioned on each side.

The ladder network 45 is connected at one end of the tape 39 to the ladder network 48 by a conducting strip 51. Similarly, the

ladder networks

46 and 47 are connected at the same end of the tape by conducting strip 52. At the other end of the tape an extension lead -3 is provided which carries on its free end four

tags

54, 55, 56 and 57. These

tags

54, 56 and 57 are required for connecting the tape to driving and selecting circuitry necessary for read-out and are connected by connecting

leads

58, 59, 61 and 62 to the free ends of the ladder networks 45, 46, 47 and 48 respectively.

The tapes are then programmed so that each stores the required two data words. Programming is the same as previously described for the tape 15 shown in FIGURE 7, that is, by punching or otherwise removing the unwanted portions of the ladder networks; the tape being fed step by step in a machine by means of the row of sprocket holes 49. After programming, each tape carries two data words of sixty bits. One word extends down ladder network 45 and up ladder network 48 and will be called the A-word on the tape. The other word extends down lad der network 46 and up ladder network 47 and will be called the B-word on the tape. Thus an A-word is read out by passing a current pulse through the ladder networks which extend from the tag 54 to the tag 57 and a B-word is read out by passing a current pulse through the ladder networks extending from tag 55 to tag 56. A few U-shaped parts 13 of the cores have been shown in position in order to indicate the position of the two rows of transformer cores on the tape and the ladder networks are shown programmed with a repetitive pattern.

Again, it is envisaged that a large number of these tapes 39 will be superimposed one upon the other so that their rows of apertures are in precise alignment and the same transformer cores can be used for all of the tapes. Connections have to be made between the driving and selecting circuitry or circuit boards and the tags on each tape. The circuit boards will be described in detail later, it being sufficient at this stage only to say that they exist. The connections can be made in one of several ways, two of which are described below.

The portion of the extension lead 53 carrying the

tags

54, 55, 56 and 57 is looped as shown in FIGURE 11 and FIGURE 12 and passed through a slot in a board 64. The tags are then flow soldered onto leads 65 from where connections can be made.

Another method is to provide pins on each tape so that they can be plugged into holes in the connector board and then soldered in position. This is the method used in this invention. FIGURE 13 shows the connecting

pins

66, 67, 68 and 69 connected to the

tags

54, 55, 56 and 57 on the extension lead 53 of a storage tape. Each pin is provided with two

lugs

71 and 72 which pass through the tape extension lead 53 and are bent over to make contact with the tag member to which the pin is to be connected. Good electrical contact is made between the pins and the tags by soldering the lugs 71 onto the tags (the solder connection is not shown). This also increases the mechanical strength of the connection.

The large number of connections that are required in a tape deck containing 128 tapes present quite a problem. The extension leads 53 of the tapes are fanned out and connections are made to more than one circuit board but even so the circuit boards would have to be larger than desired to accommodate all these connections. The solution to this problem resides in the fact that the rows of

apertures

41, 42, 43 and 44 are symmetrically positioned in the tape with respect to the row of sprocket holes 49 and to each other. That is, when two tapes are placed together with one of the tapes inverted, then the five rows of apertures still register. FIGURE 14 shows the tape deck (one hundred and twenty-eight tapes) which has been divided into two halves, each half containing the same number of tapes (sixty-four tapes). One half of the tape deck 39a is shown with the extension leads 53 uppermost while the other half 39b is shown inverted and positioned with the rows of sprocket holes 49 in precise alignment with the sprocket holes in the tapes 39a. In view of the symmetry of the tapes, the rows of

apertures

41 and 42 in the upper deck of tapes 39a are in alignment with rows of

apertures

44 and 43 in the lower deck of tapes 3%. Similarly the

rows

43 and 44 of the upper deck 39a are in alignment with

rows

42 and 41 of the lower deck 3%. FIGURE 15 is an end view of FIGURE 14 seen in the direction of the arrow A and is included in order to show the alignment of the apertures on the two halves of the tape deck. By aligning the row of sprocket holes 49 along the center of each tape the overlap shown in FIGURES 14 and 15 need not occur. It is for this reason that no overlap is shown in later figures.

The extension leads 53 can now be connected to both edges of a circuit board or circuit boards with considerably less congestion than previously. This method of stacking the tape deck presents no great problems to the driving and selection circuitry as will be apparent when the structure of the circuit boards are discussed later.

The tapes 39 are of insulating material but the ladder networks are conductive material, for example, copper. It is therefore seen that with the arrangement shown in FIGURES 14 and 15 the conductive networks on the two central tapes will be touching one another. To prevent this a single insulating sheet having identical punchings as a tape is included between the two halves 39a and 39b of the tape deck. Obviously, it is possible to put the two halves together so that the insulating surfaces of the central tapes are in contact. This would mean that the conductive patterns on the outside tapes of the deck would be exposed and liable to damage as well as the possibility of shorting occurring when the cores are in position. Thus, this arrangement would require an insulating tape on each side of the tape deck.

The dimensions of the tape 39 described above are typically as follows:

The main portion of the tape which carries the ladder networks (that is without the extension lead 53), has a length of approximately eight inches and a breadth of approximately two inches. The extension lead 53 is approximately five inches long and has a breadth of a little over half an inch. The thickness of the tape which is in this case made of polyester terephthalate is three thousandths of an inch.

When a number of tapes 39 are stacked in the store as previously explained, portions of the ladder networks on one tape are separated from the corresponding ladder networks on its neighboring tape by as little as three thousandths of an inch, this being the thickness of the tape. Thus, when a current pulse is passed along a selected ladder network or winding in the memory during information read out there is inductive and capacitive coupling between this winding and its nearest neighbors which results in damped oscillations or ringing in the selected winding. FIGURE 16 shows schematically a portion of the memory with a pattern of stored information which particularly aggravates the effect. Four cores only are shown for the purpose of illustration and are labelled A, B, C, D. Each core has its own sense winding 73 loaded by a low resistance RL and is threaded by one of two

primary windings

74 and 75. The low resistance RL is chosen so as to minimize the voltages developed in the

primary windings

74 and 75 during reading. In practice RL is so small that its value, referred to a single turn primary winding, is negligible in comparison with the leakage react-ance of the transformer. That is, the impedance measured across a primary winding 74 or 75 is the same as if the sense windings 73 were short circuited. It is assumed that primary winding 74 on one tape and primary winding 75 is in the corresponding position on the next tape in the deck. The pattern of information stored to aggravate the ringing in the memory is primary winding 74 storing 1 O 1 1 0 (which word will be referred to as word No. 1) and primary winding 75 storing O 1 0 1 0 1 (which word will be referred to as word No. 2), the third tape in the deck would be storing 1 01 0 l 0 (word No. 1) and the fourth 0 1 0 1 0 1 (word No. 2) and so on, through the store. To digress, the primary windings storing word No. 1 thread through alternate cores A, C, E, etc., and the primary windings storing word No. 2 thread through the remaining cores B, D, F, etc.

FIGURES 17b and 0 show the output signals received on a sense winding 73 in response to an input pulse (FIG- URE 17a) on a primary winding 74 or 75 for a stored binary 1 bit or a binary 0 bit respectively. It is apparent from the pulse diagrams of FIGURE 7 that the ringing which is produced on the secondary winding reduces the ratio of the 1" to 0 signals and also the maximum speed of operation. [It is therefore an undesirable effect.

The problem will now be analyzed in. order to provide a. solution. To simplify what would be an involved calculation it is assumed that there is perfect magnetic coupling between all the primary windings in the tape deck and the transformer cores threaded by them but that there is no magnetic coupling between the primary windings themselves. Thus, each primary winding behaves as though it were a single conductor and is treated as such in the following analysis.

The capacitive coupling will be greatest when the primary windings are perfectly interleaved as shown schematically in FIGURE 16. The equivalent circuit of the transformers so Wound is shown in FIGURE 18 where PQ represents any one of the primary windings that threads cores A, C, E etc., and RS represents the corresponding primary or an adjacent tape that threads cores B, D, F, etc.

To determine the response to an input current pulse I the signal generator G shown in FIGURE 18 is replaced by the three generators G G 6;, each of magnitude l/2 I as shown in FIGURE 19. This change is seen to be justified by combining the currents at points I, Q, R, and S when it is seen that the resultant currents in the circuit are still the same. Consider the response of the circuit to generators G and G only. =From considerations of symmetry these will cause no current to flow across the capacitance, and so the current in each line, PQ and RS will be 1/2 1 Now consider the response of the circuit to generator G The two lines and the distributed capacitance between them forms a transmission line with an open circuit at one end and a short circuit at the other end. This resonates at a frequency f =1/4LC and its odd harmonics, where L is the sum of the transformer leakage inductances, and C is the total capacitance between PQ and RS. Then, if I is a square pulse, having an infinite frequency spectrum all the resonant frequencies will appear on the lines. In practice the rise-time of I is made long enough for its energy content at the harmonic frequencies to be negligible in comparison with that at the fundamental, and therefore only the fundamental frequency need be considered.

From the above argument it is seen that any oscillatory current is due only to generator G and from the known properties of the transmission line its magnitude will be greatest at the short-circuit end of the line, that is through transformer cores Y and Z. Consider, therefore, the current through transformer cores Y and Z, caused by G Let these currents be respectively I and 1, These currents will be in opposite directions, as shown, and but for the negligibly small current I,,, are equal in magnitude.

As far as the voltage and currents at either end of the line are concerned, the line can be represented at frequencies up to the fundamental frequency (f by a single pi-section as shown in FIGURE 20. The capacitor at the short circuit end carries no current and can therefore be omitted, resulting in a simple parallel tuned circuit shown in FIGURE 21.

For I to be nonoscillatory the circuit must be critically damped or overdamped. This can be done by introducing a resistance :R in parallel with L or a different value of resistance R in series with L where l t m It must be remembered that, whether parallel or series damping is used, the damping must be associated with individual transformer cores or individual, primary windings, as the pattern of information stored is not generally known.

First consider parallel damping. This can be carried out by placing on each transformer core a short-circuit winding of resistance R /n where n is the total number of transformers in the memory. The damping resistors can be made in a similar manner to the tapes carrying the primary conductors. That is, a thin sheet of resistance material such as Eureka is bonded to an insulating tape (for example, a tape of polyester terephthalate). The tape and 76 and resistive coating are punched as shown in FIG- URE 22 to provide apertures 77 for the transformer cores and etched to leave a resistive loop 78 round each aperture through which the legs of the transformer cores pass. The tape 76 is also provided with a row of sprocket holes 49 for advancers in a processing machine during the formation of the resistive loops. There is some advantage in using several such resistive tapes 76 in a memory, spaced evenly throughout the stack of word tapes 39 since this gives better magnetic coupling with the cores. However, whether one resistive tape or several are used, the resistance of each closed loop 78 should be a R,,/ n where a is the number of loops linking one transformer core. As an alternative to the resistance tape, the gaps in the copper coating of each core can be coated with resistance material, thus providing the resistive loop.

Considering now the series damping, this can be produced by using resistive primary windings, but where there are many the resistance of each would have to be incon veniently high, and very high driving voltages would be necessary. For example, if each primary winding had a resistance R then, referring to vFIGURE 18 PQ and RS would each have a series resistance 2Rw/ m, where m is the total number of words in the memory.

The effective resistance appearing in series with L in FIGURE 21 would then be Rs: 4Rw/m from which Rw=mRs/ 4 In one practical example RS was approximately 120 ohms and m was two hundred and fifty-six. This gives Rw a value of 7,680 ohms and so for a current of 50 ma. through a primary winding, a voltage of 384 volts would necessarily have to be applied.

A better method of series damping is shown in FIG- URE 23. The cores marked S are the normal read-only store cores which carry the secondary windings. Each core S has associated with it a second core T, and whenever a primary winding passes through a core S, it is also taken through the associated core T. The effective resistance is introduced either by using a material with a proper loss characteristic for the T cores, or by loading them with resistive loops which can be made in the same way as the resistive loops for parallel damping.

*It has been shown above that the intertape capacitance bears a direct relationship to the ring in the transformer read-only memory. By reducing this capacitance the ringing frequency can also "be reduced. The capacitance is reduced by manufacturing three types of tapes. These tapes are the a tape shown in FIGURE 24, the b tape shown in FIGURE 25 and the c tape shown in FIGURE 26. Each of these tapes contains the same features as the tape 39 described earlier with reference to FIGURE 10. Namely, rows of

apertures

41, 42, 43 and 44, ladder networks 45, :46, 47 and 48 and sprocket holes 49. In these FIGURES 24, 25 and 26 only a portion of each tape is shown, being sufficient for the purpose of explanation.

The three tapes, a tape, b tape and c tape are identical in every respect except the ladder networks have a different stagger relative to the rows of apertures in each tape. The stagger is different longitudinally and transversely to its length, thus when the tapes are assembled in the tape deck in this order, that is a tape, b tape, tape, a tape, b tape, and so on the distance between adjacent primary windings is increased with a corresponding increase in capacitance. The programming of the tape is still carried out by punching a small hole to break the ladder network on one or the other side of the apertures as is shown in the b tape. An advantage in the programming by punching is that the same punch can be used for all three types of tape. Each tape is distinguished by a ten character figure printed in ink in box 79 on the tape. The characters indicate the tape program, its position in the module, this being the name given to the complete assembly, and its stagger.

Having thus far described the principles of the transformer read-only store, how these principles are realized in practice, some of the drawbacks, and how they have been overcome, a description of a complete module of the store will now be given. In view of the large number of parts in the complete assembly, the description that follows will be given with particular reference to four figures, namely FIGURES 27, 28, 29 and 30.

FIGURE 27, an exploded view, shows the complete module with the side of the assembly carrying the I- shaped parts 14 of the transformer cores. The U-shaped parts 13 are inserted into the array. In view of the restricted size of the drawings no serious attempt has been made to show the ladder networks on the tapes.

As previously stated the complete module of the transformer read-only store consists of one hundred and twentyeight tapes 39 arranged in two halves separated by an insulating sheet, to form the tape deck.

Each tape 39 in the tape deck carries two information words each of sixty bit length making a total capacity of two hundred and fifty-six words per module. The insulating sheet included between the two halves of the tape deck is not shown, neither is the resistive tape or tapes provided to damp ringing oscillations. The tape stagger to reduce the capacitive coupling between adjacent primary windings is not apparent in the figures.

The tape deck is mounted in an assembly which consists basically of two end blocks 82 and 83 which are spaced apart and held rigidly by two rods 84 and 85. The two end blocks are generally T-shaped and the rods 84 and 85 extend between the ends of the cross-pieces of the Ts so that a rigid rectangle is formed of similar dimensions to the main body of a tape 39, that is the portion of the tape 39 which carries the information word's. Into the underside of the cross-piece of each T-shaped end block 82 and 83 (the cross-piece is displaced laterally with respect to the stem of the T) is screwed an aligning pin 86. It is onto these two aligning pins 86 that the tape deck of the one hundred and twenty-eight tapes 39 is mounted by threading the pins 86 through the sprocket hole at each end of the tapes. The pins are of such a diameter that they just fit the sprocket holes through which they pass so that the tapes are accurately positioned with the rows of apertures in precise alignment. In view of the fact that the tapes 39 are made of very thin flexible material a sup porting tray 87 of an insulating material can be placed over the aligning pins. This tray, which is identical in construction to the main body of a tape and has the same punching, provides a firm base for the tape deck, but is not usually necessary since the tapes are. With the tape deck in position on the aligning pins the stern portion of each

end block

82 and 83 provides an abutment for the ends of the main portion of the tapes 39. The extension leads 53 from the tapes in the lower half of the tape deck pass on one side of the stem of end block 83 and the extension leads from the tape in the upper half of deck pass on the other side.

The rods 84 and 85 also provide supports for the cor carrier assemblies 88. The U-shaped parts 13 of the trans former cores are passed through the apertures in the tape deck and require no support other than a means to prevent them from dropping out again. The I-shaped parts 14, on the other hand, have to be held firmly in the correct position so that they mate with the open ends of their respective U-shaped parts 13 and form closed transformer cores. It is as a support for the I-shaped parts 14 that the core carrier assemblies 88 are provided. In the tape deck, apertures are provided for two parallel rows of transformer cores, there being thirty cores in each row. Thus thirty core carrier assemblies 88 are required, each one to carry the two I-shaped parts for the corresponding cores in the two rows.

CONCLUDING SUMMARY The invention relates to construction features for a 1 3 transformer read-only storage device, and particularly to features for eliminating the problem of oscillatory ringmg.

Stripline conductors mounted on adjacent tapes are staggered to reduce mutual capacitance.

Close conductive loops are mounted about individual transformer cores and arranged to provide critical dampingto the capacitances and inductances present.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A transformer read-only storage device having a stack of elongated insulating carriers, each carrier having a plurality of apertures spaced apart along its length in at least one row, the carriers being stacked so that the corresponding apertures register with one another; a plurality of magnetic cores passing through said registering apertures; a drive conductor for each row extending continuously along the length of the carrier and passing on one or the other side of each aperture in the row in accordance with a predetermined pattern, and sense windings one for each core arranged to receive a pattern of signals upon energization of a selected drive conductor, characterized by a varying relative displacement, from the associated row of apertures, of the corresponding drive conductors on adjacent carriers in the stack in such fashion that the distance separating a major portion of corresponding conductors on adjacent carriers is greater than the thickness of the intervening carrier, and means mounting a resistance, of critical damping value, for the capacitance and inductance present, about each of said magnetic cores.

2. A storage device according to claim 1 wherein said resistance means is an auxiliary elongated insulating carrier having a plurality of apertures spaced apart along its length which register with the existing apertures in the stack, and are similarly arranged with said cores passing through the apertures, and a closed loop of resistive material arranged about each of the apertures in said auxiliary carrier.

3. A storage device according to claim 1 wherein said resistance means is a coating of resistive material on each of said cores.

4. A storage device according to claim 1, wherein said resistance means for each core is a coating of conductive material over all of the surface of each of said cores with the exception of a narrow annulus on each core, and said narrow annulus of the surface is coated with a layer of resistive material.

5. A storage device according to claim 1, in which the plurality of apertures in each carrier extend along the length of the carrier in a plurality of rows in pairs, the drive conductors associated with each row in a pair of rows being electrically connected together at one end of the carrier and electrically connected to terminals at the other end of the carrier.

References Cited UNITED STATES PATENTS 3,138,786 6/1964 Smura 340--174 3,234,529 2/1966 Hsueh 340-174 3,245,058 4/ 1966 Bruce 340-l74 3,289,177 11/1966 Schulte 340-174 OTHER REFERENCES D. N. Taub, The Design of Transformer (Dimond Ring) Read-Only Stores, IBM Journal of Research and Development, vol. 8, September 1964, pp. 443-457.

TERRELL W. FEARS, Primary Examiner.

JOSEPH F. BREIMAYER, Assistant Examiner.