U.S. patent number 3,676,615 [Application Number 05/054,300] was granted by the patent office on 1972-07-11 for pushbutton keyboard switch array and associated printed circuit logic cards.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Fritz S. Wiedmer.
United States Patent |
3,676,615 |
Wiedmer |
July 11, 1972 |
PUSHBUTTON KEYBOARD SWITCH ARRAY AND ASSOCIATED PRINTED CIRCUIT
LOGIC CARDS
Abstract
In a keyboard, an elastic diaphragm switch array and logic,
including strobe and rollover protection. The switch includes a
diaphragm, a separator, and a switch card. The diaphragm comprises
a gold plated continuous sheet of thin spring material and serves
as a ground or voltage plane. The switch card has a gold plated pie
pattern or switch array at each key location, with generally as
many pie sections as there are bits in the code to be produced.
Each pie section is wired directly by double sided wiring and
through-holes in the switch card to the appropriate output code
pin. No decoding or encoding logic is required to produce the code.
Strobe logic is provided for assuring that all pie sections have
made contact with the diaphragm and rollover protection logic is
provided for assuring that only one key is depressed. A key button
is provided for pressing the diaphragm through the separator to
make contact with the switch card pie pattern.
Inventors: |
Wiedmer; Fritz S. (Saratoga,
CA) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
21990102 |
Appl.
No.: |
05/054,300 |
Filed: |
July 13, 1970 |
Current U.S.
Class: |
200/1R; 341/34;
200/5R; 200/517 |
Current CPC
Class: |
H03M
11/22 (20130101); H01H 13/702 (20130101); H01H
2223/002 (20130101); H01H 2207/014 (20130101); H01H
2221/064 (20130101); H01H 2221/00 (20130101); H01H
2217/016 (20130101); H01H 2221/05 (20130101); H01H
2207/016 (20130101); H01H 2207/012 (20130101); H01H
2229/032 (20130101); H01H 2239/026 (20130101); H01H
2221/024 (20130101); H01H 2221/058 (20130101) |
Current International
Class: |
H01H
13/70 (20060101); H01H 13/702 (20060101); H03M
11/22 (20060101); H03M 11/00 (20060101); H01h
009/26 (); H01h 013/52 () |
Field of
Search: |
;200/1R,5R,5E,16A,83R,86R,159B ;317/11CE |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3120584 |
February 1964 |
Grunfelder et al. |
3350518 |
October 1967 |
Krakinowski et al. |
3308253 |
March 1967 |
Krakinowski |
3382338 |
May 1968 |
Arseneault et al. |
3551616 |
December 1970 |
Juliusburger et al. |
|
Primary Examiner: Scott; J. R.
Claims
What is claimed is:
1. A keyboard apparatus, comprising:
at least one switch actuator,
an elastic diaphragm, and
a switch card;
said switch card comprising a substrate having a plurality of
arrays of switching elements and a plurality of groups of output
pins, each said element of a given array being electrically
connected by double-sided wiring on said substrate to an output pin
in a separate group:
separator means disposed between said elastic diaphragm and said
switch card for separating said diaphragm from said switching
elements when said actuator is inoperative,
said elastic diaphragm comprising a thin continuous sheet of
conductive spring material;
each said switch actuator being actuatable to deflect said
diaphragm through said separator into electrical contact with its
associated array of said switching elements, whereby an output code
is generated at said pins directly from said elements with an
output signal present at at least one output pin of each group.
2. The keyboard means of claim 1 further comprising rollover
protection logic means responsive to the output code at said pins
for detecting simultaneous electrical contact between said
diaphragm and a plurality of switching elements of different
arrays.
3. The keyboard of claim 1 further comprising strobe logic means
responsive to the output code at said pins for detecting electrical
contact between said diaphragm and all of the switching elements of
an array.
4. In an elastic diaphragm keyboard apparatus, a switch actuator
means for moving the elastic diaphragm means into contact with a
selected array of switching elements, comprising:
annular stop surface means for controlling the distance of travel
of said switch actuator means, and
actuator means integrally coupled to said surface means and
disposed along the axis thereof, for causing deflection of said
diaphragm,
said diaphragm means being deflected upon actuation of said switch
actuator means a distance equal to the protrusion of said actuator
means through said stop surface means.
5. The keyboard apparatus of claim 4 further comprising distributor
means disposed between said switch actuator means and said
diaphragm means for transmitting the actuation force from said
switch actuator means to said diaphragm means.
6. A keyboard comprising:
switch card means, having a plurality of arrays of three or more
switching element means and conductive land pattern and throughhole
means connecting said switching elements to a plurality of groups
of output connector means, with each switching element means of
each array connected to an output connector means of one of said
groups, for producing an output code,
elastic diaphragm means comprising a thin continuous sheet of
conductive spring material for providing a voltage source,
separator means disposed between said diaphragm means and said
switch card and having an opening at each array of switching
elements for electrically insulating said switching element means
and land pattern means from said diaphragm means, and
a plurality of switch actuator means, one for each of said arrays
of switching elements, for selectively deflecting said diaphragm
means through one of said openings in said separator means into
electrical contact with each said element of its associated
array,
whereby actuation of one of said switch actuator means will produce
an output signal at said output locations.
7. The keyboard of claim 6 wherein said output locations comprise a
plurality of groups of output connectors, one of said groups being
uniquely associated with a corresponding switching element from
each said array, each said switching element being connected by
double sided wiring to one and only one output connector of its
associated group.
8. The keyboard of claim 7 further comprising rollover logic means
for detecting the presence of positive logic levels at more than
one output connector of any of said groups of output
connectors.
9. The keyboard of claim 7, further comprising strobe logic means
responsive to the output code at said output connector means for
detecting that each group of output connectors has a positive logic
signal on one of its output connectors.
10. An electronic keyboard apparatus having a plurality of key
locations for generating a unique output code for each key,
comprising:
elastic diaphragm means comprising a thin sheet of conductive
spring material for providing a voltage source,
switch card means for generating an output code signal
comprising
a substrate,
a plurality of arrays of switch element means on the surface of
said substrate, one said array for each said key location, for
defining the code for said each key,
a plurality of groups of output connector means for providing the
output signal from said switch card means,
wiring means for electrically connecting said switch element means
and said output connector means with one switch element means from
each said array connected to at least one output connector means of
each of said groups,
separator means for separating said diaphragm means and said switch
card means,
a plurality of switch actuator means, one for each said key
location, for deflecting said diaphragm means through an opening in
said separator means into electrical contact with the switch
element means of its corresponding array,
rollover protection logic means for detecting simultaneous output
signals from a plurality of output connector means within a given
group, and
strobe logic means for detecting that an output signal is present
at at least one output connector means within each said group,
whereby a valid multibit output character is generated at said
groups of output connector means when one and only one switch
actuator means is actuated to move said diaphragm means into
electrical contact with all of the switch element means of its
associated array.
11. The keyboard of claim 2 further comprising strobe logic means
responsive to the output code at said pins for detecting electrical
contact between said diaphragm and all of the switching elements of
an array.
12. The keyboard of claim 8, further comprising strobe logic means
responsive to the output code at said output connector means for
detecting that each group of output connectors has a positive logic
signal on one of its output connectors.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electrical switching elements for
generating an output code, and more particularly to an array of
pressure-sensitive elastic diaphragm switching elements which are
double sided wired on a switch card to output pins and thence to
strobe and rollover protection logic.
2. Description of the Prior Art
U.S. Pat. No. 3,308,253 by M. Krakinowski, and of common assignee,
describes a diaphragm switch having a diaphragm supported on an
incompressible layer and an elastomer overlaying the diaphragm.
When pressure is applied to the elastomeric material, the
elastomeric material and the diaphragm are deformed to bring the
terminals into contact with each other. In Krakinowski, at least
two embodiments are shown: the first being one in which strips of
conducting materials are oriented perpendicular to each other and
the switching points oriented in the matrix array, and a second
embodiment where the array is constructed by coating the entire
underside of the diaphragm 18 with conducting material or using a
diaphragm of conducting material and providing an individual
conducting segment for each index position. In the latter
embodiment, a single lead is connected to the conducting layer
under the diaphragm and an individual output lead is provided for
each of the segments. Thus, in Krakinowski, each key or index
position must be determined by decoding the XY coordinates or the
single lead. It then becomes necessary, in the event that an output
code is desired, to provide logic for decoding the index point for
the given XY coordinate.
Another prior art keyboard provides a binary encoding device
including a key which selectively interconnects multiple electrical
conductors or circuits which are printed or otherwise arranged in
parallel on a flat base member. Each key includes plurality of
metallic circuit closing or shunting bars having variously spaced
projecting contact members thereon which, when actuated selectively
draw current through one or more of the parallel electrical
conductors. One severe limitation on the usefulness of this prior
art device is the number of different output pins which may be
utilized; that is, a conductive line for each output pin must pass
beneath each key position. And yet, they must not be spaced so
closely that the shunting bars cannot make distinct contact with
individual conductive lines.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an improved
pressure responsive electrical switching element.
A more specific object of this invention is to provide an improved
diaphragm, pressure-responsive switching element.
It is a further object of the invention to provide an improved
pressure-responsive diaphragm switch having a plurality of
switching elements or pie sections which are double wired to output
pins for producing an output code directly without decoding or
encoding logic.
It is a further object of the invention to provide an improved
elastic diaphragm switch keyboard with strobe logic for assuring
that all pie sections have made contact with the diaphragm.
It is a further object of the invention to provide an improved
elastic diaphragm keyboard having rollover protection logic for
assuring that only one key is depressed when transmitting the
output code.
The above objects are achieved by the invention which provides an
electronic switch means comprising at least one key button, an
elastic diaphragm means, separator means, and a switch card means.
The switch card comprises a substrate and at least one array of
switching elements or pie sections. A plurality of the switching
elements or pie sections are electrically connected by double sided
wiring on the substrate to the output pins. The elastic diaphragm
comprises a thin continuous sheet of conductive and spring material
which may be deflected by the key button through the separator into
electrical contact with the array of switching elements or pie
sections. Double sided wiring connects the pie sections to the
output pin for generation directly of the output code from the
switching array. Detection of simultaneous electrical contract
between said diaphragm and a plurality of switching elements of
different arrays is provided by rollover protection logic.
Similarly, detection of electrical contact between said diaphragm
and all of the switching elements of an array is provided by strobe
logic means.
The foregoing and other objects, features and advantages of the
invention will be apparent from the following more particular
description of preferred embodiments of the invention as
illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-section view of the key button, the elastic
diaphragm, the separator and the switch card for use in the
keyboard of the invention.
FIG. 2A shows the pattern of pie sections and conductors on the top
side of a switch card; and
FIG. 2B shows the pattern of conductors on the bottom side. The
dark dots shown on the conductive land patterns represent thru
holes for connecting the top and bottom conductors.
FIG. 2C is a logic diaphragm of the circuitry required for rollover
protection and strobing of the code generated at the output pins of
FIGS. 2A and 2B.
FIG. 3 shows the switch card array for a ten key keyboard utilizing
a 3 out of 14 code and the associated logic for strobe and rollover
protection.
FIG. 4A shows the switch card array for a 10 key keyboard and
associated rollover protection and strobe logic for generating an
EBCDIC code.
FIG. 4C describes in greater detail the Data Selector/Multiplexer
(DS/M) of FIG. 4A.
FIG. 5 is a perspective view of a console and its internal parts
illustrating the structural layout of a keyboard.
ELASTIC DIAPHRAGM SWITCH KEY CONSTRUCTION
Referring now to FIGS. 1 and 5, a description will be given of the
elastic diaphragm switch key including the button 40, diaphragm 51,
and switch card or base 60.
FIG. 5 illustrates a plurality of buttons 40 in a keyboard console
array and their relationship, in perspective view, to the various
layers 50-54, and 60 shown in sectional view in FIG. 1.
Key button (or actuator means) 40 is a round button shown in
cross-section through the center line in FIG. 1. Finger area 41 of
the button is shown concave but may also be convex, flat, sunk into
the face plate 30, flush with or raised above the face plate 30.
Face plate 30, layers 50-54 and 60, logic card 55, are mounted as
by screws (not shown) in base 56. The outside diameter or gliding
surface 42 of button 40 rides within the hole 31 in face plate 30.
Hole 31 further includes a cone area 32, a ledge area 33, and a
larger diameter surface 34. Cone area 32 serves to reduce the area
of contact between the hole 31 and the button 40, ledge 33 prevents
the button 40 from moving upwards out of hole 31.
Button 40 further includes an annular ball portion 44 having a well
portion 43 for catching dirt, etc., that may fall between hole 31
and button surface 42. Annular ball section 44 is in the form of a
spherical ball when viewed as shown in FIG. 1 for allowing the
button 40 to rotate only around the center of the ball 44 and thus
prevent binding of the button 40 between surface 42 and hole
surface 31. The bottom surface of annular ball 44 comprises a
button actuator stop surface 45 for preventing damage to the
elastic diaphragm 51 and for giving the desirable
force/displacement curve for the actuator 46.
Actuator 46 extends a distance W beneath the surface of annular
stop 45, and in cooperation therewith gives a reliable or
repeatable actuation of the elastic diaphragm independent of the
finger force characteristics of the keyboard operator.
Distributor layer 50 has several functions. It protects the elastic
diaphragm from hard actuation by actuator 46 directly, and from any
rough spots on said actuator. The fact that the travel of actuator
46 into the separator 50 is limited by the stop surface 45 further
protects the elastic diaphragm layer 51 from accidental or
malicious blows on the button 40.
The actuator 46 plays a material role in the determination of the
force/displacement characteristics. Its length W determines the
button stoke and its diameter together with the hardness and
thickness of the separator layer 50 determines the button force.
Thus, a soft and thick distributor 50 gives a light, long button
stroke, and vice versa. In general, the softness and thickness of
distributor 50 and the dimension W have to be increased and
decreased together. But the precise relative selection allows a
light button to have a long stroke, or allows a button of any
stroke to be made with a lighter or harder touch. Of course, the
shape of actuator 46 (that is, whether it is round or flat on the
bottom) also plays a role in the force/displacement characteristics
of the button, as do the physical characteristics of the elastic
diaphragm area 51 and the separator layer 52. Finally, another
function of the distributor 50 is to produce a force on the
diaphragm 51 that spreads from the center (i.e., the center line of
button 40) to the edge and does so over a finite length of the
button travel while at the same time increasing the force from the
center to the edge.
The feature of a key button 40 of the design shown with a actuator
46 and a distributing ring 45 together with a relatively thick,
soft distributor 50 permits repeated, reliable operation of the
key. The key further includes a separator layer 52 having an
opening V through which the elastic diaphragm 51 is pressed into
contact with the array of pie sections (that is, switching
elements) on the top surface of switch card 60. The bottom and top
surfaces of switch card 60 have conductive land patterns deposited
or otherwise provided thereon and via holes as necessary to
interconnect the top and bottom land patterns, as will be described
in connection with the preferred embodiments of keyboards to be
described hereinafter.
Isolator section 53 isolates the switch card 60 from the back plate
54. Logic card 55 is shown herein, positioned between plate 54 and
base 55. The various layers 50, 51, 52, 60, 53, and 54 may be
merely placed upon each other and held together by screws or other
mechanical fasteners as will be obvious to those skilled in the
art.
Diaphragm 51 comprises, for example, 1/2 to 1 mil Berylco 25 (a
beryllium copper spring alloy) plated with 150 micro inches of
gold. Varying the thickness of the Berylco 25 in the copper varies
the actuating force of the switch very little. The actuating force
is determined by the distributor-actuator combination and the
separator thickness.
Separator 52 comprises two to three mils of Mylar, with three mils
preferred because it tends to make the switch less sensitive to
imperfections in the bottom surface of diaphragm 51. Together with
a quarter inch hole in the separator 52, the three mils thickness
Mylar separator 52 makes a sensitive switch that keeps stresses in
the diaphragm 51 low.
Herein, switch card 60 comprises a base of copper clad epoxy board.
Isolator 53 comprises, for example, 3 mils Mylar, which is not
necessary of course if back plate 54 is non-conductive. Said back
plate 54 is optionally provided to re-enforce the switch card 60
against abuse.
Referring now to FIGS. 2A and 2B, one preferred embodiment of the
invention for an elastic diaphragm switch key board array will be
described. FIG. 2A represents a land pattern on the "Y" side of a
switch card (refer to FIG. 1) which will be contacted by the
elastic diaphragm. FIG. 2B represents a pattern of conductors on
the "Z" side of the switch card (refer to FIG. 1), opposite from
the elastic diaphragm. FIGS. 2A and 2B are viewed from the same
position, such that the output pins 61 through 68 appear in the
same orientation in both figures. Each key position is represented
in FIG. 2A by an array of four squares. These are the switching
elements or pie sections. The dark lines 68A, 74A, etc. represent
conductors, and the dark dots V15, V49, etc. represent via holes
connecting the conductors of FIG. 2B with the conductors or square
contacts of FIG. 2A. The four square key contact areas for each key
position are electrically insulated from each other. The upper
right-hand square, or pie position 8, represents the eight bit; the
lower right-hand square, or pie position 4, the four bit; the upper
left-hand square, or pie position 2 the two bit; and the lower
left-hand square or pie position 1, the one bit position. The upper
right-hand square of each key position is wired to either output
pin 68 or 78. The lower right-hand square of each key position is
wired to either output pin 64 or 74. The upper left-hand square of
each key position is wired to either output pin 62 or 72, and the
lower left-hand square of each key position is wired to either
output pin 61 or 71. Output pin 63 is wired to pad 73 which is held
in continuous contact with the voltage plane or elastic diaphragm.
Table 1 shows the interconnection performed by each via hole V-1
through V-57. The bottom connection column refers to the conductor
on the bottom, that is in FIG. 2B. The top connection column
represents the conductor or the square pie section to which the via
hole interconnects the related bottom conductor. The top connection
column is interpreted as follows: Where the via hole are starred as
is V-13, V-16, etc., the top connection is to a conductive line
such as 62a, 72a, 71a, etc. The other via holes are connected to
one of the pie positions at each key location: for example, V-1 is
connected to key position D, pie section 2; via V-2 is connected to
key position D pie position 1, and so forth.
TABLE 1
Via Hole Connections, FIG. 2.
Top Bottom Via Hole Connection Connection (Line or (Line) pie
section) V1 8D2 72b V2 8D1 71b V3 8B2 72b V4 8B1 71b V5 8Z2 72b V6
8Z1 71b V7 8N2 72b V8 8N1 61b V9 8B4 74b V10 8Z4 74b V11 8M2 72b
V12 8M1 61b V13* 62a 62b V14 872 62b V15 871 61b V16* 72a 72b V17
882 72b V18 881 71b V19* 71a 71b V20 892 72b V21 891 61b V22 8M8
68b V23 888 68b V24 898 68b V25 8E2 62b V26 8E1 71b V27* 62a 62b
V28 842 72b V29 841 71b V30* 62a 62b V31* 72a 72b V32 852 72b V33
851 61b V34* 71a 71b V35 862 62b V36 861 71b V37 8E4 64b V38 844
64b V39 854 64b V40 864 64b V41 8R2 62b V42 8R1 61b V43 812 72b V44
811 61b V45* 72a 72b V46* 62a 62b V47 822 62b V48 821 71b V49* 71a
71b V50 832 62b V51 831 61b V52 8R4 64b V53 818 78b V54 828 78b V55
824 74b V56 838 78b V57 834 74b
Referring further to FIG. 2A and 2B, in connection with Table 2,
below, the output code for the key board of FIG. 2 will be
explained. A 16-key key board is shown having hexidecimal output
values zero through F. The various keys are 8B, 81, 82, 83, 84, 85,
86, 87, 88, 89, 8Z, 8N, 8D, 8M, 8E, 8B. The binary value appearing
at the output pins 6Z1-678, is shown in the column entitled Binary
Value of Output. Thus, a zero in the 8 column indicates a positive
logic on pin 78, a 1 in the 8 column represents a positive logic on
pin 68, a zero in the 4 column of the table indicates a positive
logic on pin 74, a 1 in the 4 column indicates a positive output on
line 64, a zero in the 2 column represents a positive logic level
on output pin 72, a 1 in the 2 column represents a positive logic
level on pin 62, a zero in the one column represents a positive
logic on output pin 71, and a 1 in the one column represents a
positive logic on output pin 61.
Thus, by depressing the D key to bring the elastic diaphragm
voltage plane into contact with switch array 8D, the hexidecimal
output code of zero will be detected as positive logic level on
output pins 71, 72, 74, and 78, and negative logic level on output
pins 61, 62, 64, and 68. Similarly, by bringing the key array 85
into contact with the voltage plane, a hexidecimal 5 output is
detected as a positive logic on output pins 64, 61, 78 and 72.
TABLE 2
Output Code for Keyboard of FIG. 2.
Binary Value of Output Key Hexidecimal 8 4 2 1
__________________________________________________________________________
8B 0 0 0 0 0 81 1 0 0 0 1 82 2 0 0 1 0 83 3 0 0 1 1 84 4 0 1 0 0 85
5 0 1 0 1 86 6 0 1 1 0 87 7 0 1 1 1 88 8 1 0 0 0 89 9 1 0 0 1 8Z A
1 0 1 0 8N B 1 0 1 1 8D C 1 1 0 0 8M D 1 1 0 1 8E E 1 1 1 0 8R F 1
1 1 1
__________________________________________________________________________
it is thus apparent from the above described embodiment of the
invention, that the desired hexidecimal output code is produced
directly at the output pins 61 through 78. Proceeding now to FIG.
2C, a description will be given of the circuitry required for
rollover protection and strobing. Rollover protection is defined as
the detection of the simultaneous depression of two keys. Strobing
is defined as the detection of a contact closure occurring at each
of the pie positions in a given key array. Referring now to FIG.
2C, the output pins 61 through 78 of FIGS. 2A and 2B are shown. The
logic of FIG. 2C may be physically located on logic card 55 (FIG.
5). Output pin 61 is connected to Exclusive OR 11. Output pin 71 is
connected to Exclusive OR 11 and AND 16. Output pin 62 is connected
to Exclusive OR 12. Output pin 72 is connected to Exclusive OR 12
and AND 17. Output pin 64 is connected to Exclusive OR 13. Output
pin 74 is connected to Exclusive OR 13 and to AND 18. Output pin 68
is connected to Exclusive OR 14. Output pin 78 is connected to
Exclusive OR 14 and AND 19. The outputs of Exclusive OR's 11
through 14 are connected to AND 15, the output of which is
connected to AND's 16 through 19. The inputs to AND 15 are
satisfied such that there is a positive logic output therefrom only
if the output of each Exclusive OR 11 through 14 is positive. This
occurs only when one and only one pin of each the following pairs
of outputs pins are positive: 61 and 71, 62 and 72, 64 and 74, and
68 and 78. Thus, a positive output from AND 15 indicates that one
and only one key on the key board of FIG. 2A has been depressed.
The voltage levels on pins 56-59 are decoded directly to the binary
values of Table 2.
Referring now to FIG. 3, the switch card array for a ten key
keyboard utilizing a three out of fourteen code and the associated
logic for strobe and roll-over protection will be described. The
various pie sections A, B, and C for the various switch key
locations 90 through 99 are wired by double-sided wiring, described
above, to the various output pins 2A0 through 2C3. For sake of
simplicity, only the switch arrays 90-99 of the ten key numeric
portion of a much larger keyboard is shown, while the logic for the
full keyboard is shown. The connections from the various keys 90-99
to the output locations 2A0-2C3 are shown in heavy and dotted
lines: the heavy lines being on one side of said switch card and
the dotted lines on the other side. It will be apparent to those
skilled in the art, that various other wiring schemes may be
utilized to connect the various pie sections A, B, and C to the
output pins 2A0-2C3. The heavy dots at the connection of dotted
lines to solid lines or at the connection of dotted lines to pie
sections at the various key locations represent through holes,
while the heavy dots between solid lines and the pie sections
merely indicate connections between the land pattern conductors and
the pie sections which are on the same side of the switch card.
Herein, all of the output pin locations 2A0 through 2C3 are
connected to positive voltage. The elastic diaphragm is at ground
voltage, herein, and is shown as element 50A, diagrammatically.
The roll-over protection logic, as will be described more fully
hereinafter, comprises inverters 431 through 444, AND circuits 451
through 464, OR circuits 465 through 467, and AND circuit 468. As
will be apparent more fully hereinafter, the 3 of 14 output code
generated by actuating one of the keys at key positions 90-99
appears directly at output pins 2A0 to 2C3, while a signal at pin
470 indicates that only one key has been actuated, and that all of
the pie sections of that key have made contact with diaphragm 51A,
thus signaling that a valid code exists at output pins 2A0-2C3.
First, the output code generated by the various keys 90-99 at
output pins 2A0-2C3 will be described, followed by description of
the strobe and roll-over protection circuitry of FIG. 3.
First it should be noted that the A pad of each key 90-99 is
connected to one and only one of output pins 2A0-2A4. The B pad of
each key location 90-99 is connected to one and only one of output
pins 2B0-2B4. And finally, the C pad at each key location 90-99 is
connected to one and only one of output pins 2C0-2C3. Thus,
actuation of key 90 causes a positive logic signal to appear at
output pin 2B2, and 2A4, and 2C0. The following Table 3 summarizes
the connection between the various pie or switch locations A, B,
and C of each key (or switch array) to output pins 2A0-2C3.
TABLE 3
Summary of Connections: Key Locations to Output Pins for FIG. 3
Key Location Pie Section or Output Switch Location 90 90A 2A4 90B
2B2 90C 2C0 91 91A 2A1 91B 2B1 91C 2C0 92 92A 2A1 92B 2B2 92C 9C0
93 93A 2A1 93B 2B3 93C 2C0 94 94A 2A2 94B 2B1 94C 2C0 95 95A 2A2
95B 2B2 95C 2C0 96 96A 2A2 96B 2B3 96C 2C0 97 97A 2A3 97B 2B1 97C
2C0 98 98A 2A3 98B 2B2 98C 2C0 99 99A 2A3 99B 2B3 99C 2C0
Thus, from Table 3 and FIG. 3, it becomes apparent that actuation
of key 90 gives an output code comprising positive logic signals at
output pins 2A4, 2B2, 2C0. Similarly, actuation of key 94 causes an
output code to appear in the form of contact closures at pins 2A2,
2B1, and 2C0.
Referring again to FIG. 3 the strobe and roll-over protection
circuitry will be described. Output pin 2A0 is connected to
inverter 431, and to AND circuits 452 through 455.
Output pin 2A1 is connected to inverter 432 and AND circuits 451,
453, 454, and 455. Outpin pin 2A2 is connected to inverter 453 and
to AND circuits 451, 452, 454, and 455. Output pin 2A3 is connected
to inverter 434 and to AND circuits 451, 452, 453, and 455. Output
pin 2A4 is connected to inverter 435, and to AND circuits 451
through 454.
Output 2B0 is connected to inverter 436, and to AND circuits 457
through 460. Output pin 2B1 is connected to inverter 437 and to AND
circuits 456, 458, 459, and 460. Output pin 2B2 is connected to
inverter 438, and to AND circuits 456, 457, 459, and 460. Output
pin 2B3 is connected to inverter 439, and to AND circuits 456, 457,
458, and 460. Output 2B4 is connected to inverter 440, and to AND
circuits 456 through 459.
Output pin 2C0 is connected to inverter 441 and to AND circuits 462
through 464. Output pin 2C1 is connected to inverter 442 and to AND
circuits 461, 463, and 464. Output pin 2C2 is connected to inverter
443, and to AND circuit 461, 462, and 464. Output pin 2C3 is
connected to inverter 444, and to AND circuits 461 through 463.
Inverter 431 is connected to AND circuit 451, inverter 432 to AND
452, inverter 433 to AND 453, inverter 434 to AND 454, inverter 435
to AND 455, inverter 463 to AND 456, inverter 437 to AND 457,
inverter 438 to AND 458, inverter 439 to AND 459, inverter 440 to
AND 460, inverter 441 to AND 461, inverter 442 to AND 462, inverter
443 to AND 463, and inverter 444 to AND 464. The inputs to OR 465
are the outputs of ANDs 451 through 455, the inputs to OR 466 are
the outputs of ANDs 456 through 460, and the inputs to OR 467 are
the outputs of ANDs 461 through 464. The outputs of OR circuits 465
through 467 are fed to AND circuit 468, the output of which appears
at pin 470. A signal at pin 470 indicates strobe and no
roll-over.
Referring now to FIG. 4A, a description will be given of a keyboard
and logic for generating an EBCDIC code wherein each pie position
of each key determines two bits in the output code according to the
following table:
TABLE 4
Output Code and Wiring for EBCDIC Keyboard of FIG. 4A
Key Output Pin Locations for Pad Output Code Position A B C D A B C
D 12 34 56 78
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20 1A3 1B3 1C0 1D0 11 11 00 00 21 1A3 1B3 1C0 1D1 11 11 00 01 22
1A3 1B3 1C0 1D3 11 11 00 10 23 1A3 1B3 1C0 1D3 11 11 00 11 24 1A3
1B3 1C1 1D0 11 11 01 00 25 1A3 1B3 1C1 1D1 11 11 01 01 26 1A3 1B3
1C1 1D2 11 11 01 10 27 1A3 1B3 1C1 1D3 11 11 01 11 28 1A3 1B3 1C2
1D0 11 11 10 00 29 1A3 1B3 1C2 1D1 11 11 10 01
__________________________________________________________________________
the above table, giving the output code and wiring scheme for the
EBCDIC keyboard of FIG. 4A, may be correlated with FIG. 4A in the
following manner. Actuation of the key which brings switch array 20
into contact with ground plane or elastic diaphragm 51B causes a
positive logic signal to appear at output pin locations 1A3, 1B3,
1C0, and 1D0. This gives an output code of 11110000. The wiring
from key 20 to said output pins is by double-sided wiring, as shown
in FIG. 4A, where the switch locations or pie positions and the
wiring on the same side of the switchcard as said pie positions are
shown in solid lines, with the dark dots representing via holes
between said conductors and pie positions to the dotted lines
representing conductors on the opposite side of said switch card.
Thus, pie section B of switch array 20 is connected by a solid line
to output pin 1B3, pie sections A and D are connected by double
sided wiring (shown by dotted and solid lines) to pads 1A3, and 1D0
and pie section C is connected by single side wiring to its output
pin 1C0.
While actuation of a given key results in direct generation of
sixteen bit code at output pins 1A0-1D3, herein the code at said
pins is further decoded to give an eight-bit output code at pins
310, 320, 330, 340, 350, 360, 370, and 380 of FIG. 4A. The same
decoding logic for giving the eight-bit output code is utilized for
the strobe and rollover protection in the manner to be described
hereinafter. Referring again to the TAble 4 in connection with FIG.
4A, output code bits 1 and 2 are determined by the state of output
pins 1A0, 1A1, 1A2, and 1A3. Output code bits 3 and 4 are
determined by the state of output pins 1B0-1B3. The bits 5 and 6 of
the output code are determined by the state of output pins 1C0-1C3,
and the state of bits 7 and 8 of the output code are determined by
the condition of output pins 1D0-1D3. For each set, that is, the A,
B, C, or D set of pins, the associated two bits in the output code
will be zero if the zero (i.e., 1A0, 1B0, 1C0, or 1D0) pin is at a
positive logic level, or "on." if the 1 pin is on, the associated
output code bits will be 01. If the 2 pin is on, the associated
output code bits will be 10. And finally, if the 3 output pin is
on, the associated output code bits will be 11. In the above
manner, output pins 1A0-1A3 on the switchcard control the state of
output pins 310 and 320 representing bits 1 and 2, respectively.
Bits 1 and 2 will be 00 if 1A0 pin is on, 01 if 1A1 pin in on, 10
if the 1A2 pin is on, and 11 if the 1A3 pin is on.
As in FIG. 3, FIG. 4A shows the switch array or key locations for
only 10 keys of a much larger keyboard, but the logic shown is for
the entire keyboard.
Referring now to FIG. 4A, the manner in which the output pins
1A0-1D3 are decoded to provide the rollover protection, strobe, and
the eight-bit EBCDIC code will next be described. The Data
Selector/Multiplexor, DS/M 211 shown in FIG. 4A is shown in greater
detail in FIG. 4B and will be described hereinafter. Suffice it to
say at this time, that the outputs of any DS/M will be negative if
and only if one of the four inputs is positive. The OR inverters,
OI will have a positive output when either but not both of its
inputs is positive. An inverter I inverts the signal at the input.
An AND inverter AI gives a negative output when all of its inputs
are positive. A single shot SS gives a timed positive output
whenever its input goes positive. A negative OR inverter -OI gives
a negative output when one but not both of its inputs are negative.
Parity generator PG gives a positive output when an even number of
its inputs are positive, and a negative output when an odd number
of its inputs are positive.
Proceeding now with a description of the logic flow of FIG. 4A,
output pin 1A0 is connected to DS/M 211. Output pin 1A1 is
connected to DS/M 211 and OI 272. Output pin 1A2 is connected to
DS/M 211 aNd OI 271. Output pin 1A3 is connected to DS/M 211, OI
271, and OI 272. Output pin 1B0 is connected to DS/M 212. Output
pin 1B1 is connected to DS/M 212 and OI 274. Output pin 1B2 is
connected to DS/M 212 and OI 273. Output pin 1B3 is connected to
DS/M 212, OI 273, and OI 274. Output pin 1C0 is connected to DS/M
213. Output pin 1C1 is connected to DS/M 213 and OI 276. Output pin
1C2 is connected to DS/M 213 and OI 275. Output pin 1C3 is
connected to DS/M 213, OI 275, and OI 276. Output 1B0 is connected
to DS/M 214. Output pin 1D1 is connected to DS/M 214, and OI 278.
OUtput pin 1D2 is connected to DS/M 214 and OI 277. Output pin 1D3
is connected to DS/M 214, OI 277, and OI 278.
Herein, all of the output pins 1A0 through 1D3 are connected to
positive voltage.
The output of DS/M 211 is inverted by I 215 and fed to AI 219. The
output of DS/M 212 is inverted by I 216 and fed to AI 219. The
output of DS/M 213 is inverted by I 217 and fed to AI 219. The
output of DS/M 214 is inverted by I 218 and fed to AI 219. Thus, a
negative output of any DS/M is inverted and appears as a positive
input to AI 219. The output of AI 219 will be positive, therefore,
when one and only one of the A pins, one and only one of the B
pins, one and only one of the C pins, and one and only one of the D
pins are at a positive logic level. The output of AI 219 is fed to
single shot 220, the output of which appears on rollover protection
line 210, which line 210 has a positive logic level when one and
only one of the keys 20-29 are in contact with the ground plane or
elastic diaphragm 51B.
The output of single shot 220 is also fed bit gates to AI 301-308.
The output of OI 271 is fed to AI 301, of OI 272 to AI 302, of OI
273 to AI 303, of OI 274 to AI 304, of OI 275 to 305, of OI 276 to
AI 306, of OI 277 to AI 307, and of OI 278 to AI 308. Thus, the
various bit gates 301-308 have a positive output when one and only
one key has been made as signaled on line 210 and the corresponding
bits 1 through 8 has been decoded from the output pins 1A0-1D3 by
the OR inverters 271-278. The output of the bit gates, AI's 301-308
are held in the corresponding bit latches, comprising a -OI and an
AI, until the latches are restored by a signal at pin 300.
Similarly, rollover protection is held in the bit latch comprising
-OI 230 and AI 260 to hold output pin 390 at a logic level
indicating strobe and inviting the using logic (not shown) to
accept the output code appearing on pins 310-380.
Thus, the output of single shot 220 is fed to -OI 230, thence to AI
260, and strobe output pin 390. The output of AI 301 is fed to -OI
311, thence to AI 321 and to bit 1 output pin 310. The output of AI
302 is fed to -OI 312, thence to AI 322 and to bit 2 output pin
320. The output of AI 303 is fed to -OI 313, thence to AI 323 and
to bit 3 output pin 330. The output of AI 304 is fed to -OI 314,
thence to AI 324 and to bit 4 output pin 340. The output of AI 305
is fed to -OI 315, thence to AI 325 and thence to bit 5 output pin
350. The output of AI 306 is fed to -OI 316, thence to AI 326 and
thence to bit 6 output pin 360. The output of AI 307 is fed to -OI
317, thence to AI 327 and thence to bit 7 output pin 370. The
output of AI 308 is fed to -OI 318, thence to AI 328 and thence to
bit 8 output pin 380. The output of AI's 321-328 are also fed to
parity generator 329, the output of which appears at pin 331. The
restore line signal appearing at 300 is fed to AI 260, and AI
321-328. The output of AI 260 is fed back to -OI 230. The output of
AI 321 is also fed back to -OI 311. The output of AI 322 is also
fed back to -OI 312. The output of AI 323 is also fed back to -OI
313. The output of AI 324 is also fed back to -OI 314. The output
of AI 325 is also fed back to -OI 315. The output of AI 326 is also
fed back to -OI 316. The output of AI 327 is also fed back to -OI
317. And, the output of AI 328 is also fed back to -OI 318.
With the logic above described and shown in FIG. 4A, a signal
appearing at output pins 1A0-1D3 representing the closure of
contacts comprising the pie sections of a given key location 20-29
and the elastic diaphragm ground plane 51B, are decoded to an
eight-bit code at pins 310-380, and roll-over protection and strobe
signals are generated at lines 210 and 390.
Referring now to FIG. 4B, a more detailed description will be given
of Data Selector/Multiplexor 211 of FIG. 4A. The other DS/M's
212-214 are similarly wired to perform similar functions, as will
be apparent to those skilled in the art. Referring now to FIG. 4B,
a negative signal appears at output line 261 when one and only one
of pins 1A0-1A3 are connected to ground by closure of the
corresponding switch. Said switches are shown to represent the pie
sections A at the various switch arrays 20-29. Pin 1A0 is connected
to inverter 221, pin 1A1 is connected to inverter 222, pin 1A2 is
connected to inverter 223, and pin 1A3 is connected to inverter
224. The connections to inverters 221-224 represent the four input
lines shown at the inputs to DS/M211 through 214 in FIG. 4A. Not
shown in FIG. 4A are the wiring locations E, E0, E15, Wiring
locations E7, E11, E13, and E14 are held at a positive voltage
through resistance R1. On the other hand, wiring locations E,
E0-E6, E8-E10, E12, and E15 are tied to ground.
The ground voltage appearing at wiring location E is inverted by I
229 and fed to AND circuits 231-246. This signal would serve to
enable all of said AND circuits 231-246. However, the ground
voltage at wiring location E0 is fed to AND 231, thus effectively
disabling said AND circuit 231 from operation. Similarly, and for
the same function, the ground voltage at wiring location E1 is fed
to AND circuit 232, at E2 is fed to A 233, at E3 is fed to AND
circuit 234, at E4 is fed to AND circuit 235, at E5 is fed to AND
circuit 236, at E6 is fed to AND circuit 237, at E8 is fed to AND
circuit 239, at E9 is fed to AND 240, is fed to AND circuit 241, at
E12 is fed to AND 243, and at E15 is fed to AND circuit 246. On the
other hand, positive voltage at wiring location E7 is fed to AND
circuit 238 to enable said AND circuit 238. Similarly, the positive
voltage at E11 is fed to AND circuit 242, at E13 is fed to AND
circuit 244, and at E14 is fed to AND circuit 245.
The output of inverter 221 is fed along line 252 to AND circuits
231, AND circuit 233, AND circuit 235, AND circuit 237, AND circuit
239, AND circuit 241, AND circuit 246, and AND circuit 245. Also,
the output of inverter 221 is fed through inverter 225 and thence
along line 253 to AND circuit 232, 234, 236, 238, 240, 242, and 244
and 246.
The output of inverter 222 is fed along line 254 to AND circuits
A231, 232, 235, 236, 239, 240, 243, and 244. Also, the output of
inverter 222 is fed through inverter 226 along line 255 to AND
circuits 233, 234, 237, 238, 241, 242, 245, and 246.
The output of inverter 223 is fed along line 256 to AND circuits
231-234, and 239-242. The output of inverter 223 is also fed
through inverter 227 along line 257 to AND circuits 235-238 and
243-246. The output of inverter 224 is fed along line 258 to AND
circuits 231-238. Also, the output of inverter 224 is fed through
inverter 228 along line 259 to AND circuits 239-246. The output of
AND circuits 231-246 are fed to OR circuit 250, the output of which
appears at output pin location 261. With the arrangement shown in
FIG. 4B, a negative signal will appear at output pin 261 when one
and only one of the inputs to inverters 221-224 is positive.
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 the foregoing and other changes in
forms and details may be made therein without departing from the
spirit and scope of the invention.
* * * * *