Circuit arrangement for an input keyboard

• US 4,251,805 A
• Filed: 12/13/1978
• Issued: 02/17/1981
• Est. Priority Date: 12/17/1977
• Status: Expired due to Term

• Current Assignee: ITT Industries Inc (ITT, Inc.)
• Original Assignee: ITT Industries Inc (ITT, Inc.)
• Inventors: Holzmann, Dieter, Grosse, Joachim
• Primary Examiner(s): Groody, James J.
• Application Number:
  US05/969,050
• Time in Patent Office: 797 Days
• Field of Search: 340/365 R, 340/365 E, 340/365 S, 178/17 C, 178/17 A, 179/90 K, 400/472, 400/479
• US Class Current: 341/29
• CPC Class Codes: H03M 11/22 Static coding H03M11/26 takes precedence

Abstract

A keyboard switch matrix has a plurality of column and row wires and switches having only two poles and no interconnecting diodes for selectively connecting one of said columns to one of said rows. Associated with each column and row wire is a flip-flop having a set input connected to the wire and an electronic switch for each flip-flop connecting a flip-flop output to the set input. The outputs of the row flip-flops are connected to a NOR-gate, the output of which is connected to a control input of the electronic switches associated with the column flip-flops and also to a second set input of the column flip-flops. The output of the NOR-gate is further connected to a control input of the electronic switches associated with the row flip-flops through an inverter. Reset inputs of the column flip-flops are connected to the NOR-gate output through a differentiation circuit which is triggered by a negative pulse edge. A second NOR-gate has its inputs connected to the column wires and provides an output to a differentiation circuit which is triggered by a positive pulse edge. The output of the differentiation circuit is connected to reset inputs of the row flip-flops. Thus, the geometric position of the actuated keyboard switch is stored in the respective row and column flip-flops, and code signals corresponding to said position are provided at the outputs of said flip-flops.

Claims

1. A circuit arrangement for an input keyboard of electronic equipment comprising two-terminal key switches arranged in m columns and n rows, with each key switch, upon actuation, directly connecting a column lead associated with the respective column, to a row lead associated with the respective row, and the circuit arrangement, with respect to the columns, transmitting a one-out-of-m code signal and, with respect to the rows, a one-out-of-n code signal, wherein the improvement comprises:

one row flip-flop for each row, each row flip-flop including one reset, one set input, and an output associated with the set input, said set input being connected to the respective row lead;

one first make contact type electronic switch for each row flip-flop connecting the set input thereof to the output associated with the set input and having a control input;

a first NOR-gate having an output and n inputs which are arranged at the output of each row flip-flop associated with the respective set input;

a first differentiating circuit having an output and an input connected to the output of the first NOR-gate, and which is triggered by a negatively directed pulse edge;

an inverter stage having an output and an input, said inverter input being connected to the output of the first NOR-gate and said inverter output being connected to all control inputs of the first electronic switches;

one column flip-flop means for each column, each column flip-flop means having one reset input and two set inputs not conditioning one another of which the first one is connected to the respective column lead and the second one is connected to the output of the first NOR-gate with the column flip-flop means reset input being connected to the output of the first differentiating circuit, each column flip-flop means also having an output associated in common with the two set inputs;

one second make contact type electronic switch for each column flip-flop means, connecting the first set input thereof to the output associated in common with the two set inputs, and having a control input connected to the output of the first NOR-gate;

a second NOR-gate having an output and m inputs applied to the respective first set input of the column flip-flop means;

a second differentiating circuit having an input connected to the output of the second NOR-gate, and an output connected to all reset inputs of the row flip-flops, said second differentiating circuit being triggered with the aid of a positively directed pulse edge; and

a highly resistive termination of each column lead, whereby the code signals are provided at the outputs of the respective row flip-flop and column flip-flop means.

2. A circuit arrangement for an input keyboard comprising:

first switch means for selectively connecting one of m-columns to one of n-rows;

means associated with each column and each row for storing a signal associated with each column and row;

second switch means for switching said stored signals between an input and output of each of said storing means;

first logic means for providing NOR logic from the outputs of said row storing means, said NOR logic applied to said second switch means for switching of said row storing means through a means for inverting, said NOR logic being further applied to said column storing means and to said second switch means and to said column storing means through a first differential circuit for switching of said column storing means; and

second logic means for providing NOR logic from the m-columns, said NOR logic applied to said row storing means through a second differential circuit, where the keyboard signal may be derived from the outputs of said storage means.

3. The circuit of claim 2 wherein said first switch means upon actuation connects a column lead associated with a respective column to a row lead associated with a respective row.

4. The circuit of claim 3 wherein the column lead transmits a one-out-of-m code signal and the row lead transmits a one-out-of-n code signal.

5. The circuit of claim 2 wherein said row storing means comprises a plurality of flip-flops each having a set input and a reset.

6. The circuit of claim 2 wherein said column storing means comprises a plurality of flip-flop means each having two set inputs and a reset.

7. The circuit of claim 2 wherein said second switch means for switching includes a plurality of control inputs.

8. The circuit of claim 7 wherein said first logic means NOR logic as applied through said means for inverting is connected to said control inputs of said second switch means for switching of said row storing means.

9. The circuit of claim 6 wherein said first logic means NOR logic as applied through said first differential circuit is applied in said resets.

10. The circuit of claim 7 wherein said first logic means NOR logic is applied to said control inputs of said second switch means for switching said column storing means.

11. The circuit of claim 5 wherein said second logic means NOR logic as applied through said second differential circuit is applied to said reset of each said row storing means flip-flops.

12. A circuit arrangement for an input keyboard comprising:

first means for switching arranged in m-columns and n-rows, each of said first switching means connecting a respective row with a respective column;

means for each column and each row for storing a signal associated with each column and each row, each said storing means having a set input and a reset;

second switch means for switching said stored signal between an output and said input of each of said storing means;

first means for providing NOR logic from the outputs of said row storing means, said NOR logic applied to said second means for switching of said row storing means through an inverter, applied to said reset of said column storing means through a first differential circuit, and applied to said second means for switching of said column storing means and said set input of said column storing means; and

second means for providing NOR logic from the m-columns, said second means NOR logic applied to said reset of said row storing means through a second differential circuit, whereby the keyboard signals may be derived from the outputs of said storing means.