JPS56155437A - Key code reading circuit - Google Patents

Key code reading circuit

Info

Publication number
JPS56155437A
JPS56155437A JP5963980A JP5963980A JPS56155437A JP S56155437 A JPS56155437 A JP S56155437A JP 5963980 A JP5963980 A JP 5963980A JP 5963980 A JP5963980 A JP 5963980A JP S56155437 A JPS56155437 A JP S56155437A
Authority
JP
Japan
Prior art keywords
key code
amplifiers
key
reading circuit
lines
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP5963980A
Other languages
Japanese (ja)
Other versions
JPS6242288B2 (en
Inventor
Kikuya Soma
Hiroshi Morito
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
Nippon Electric Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NEC Corp, Nippon Electric Co Ltd filed Critical NEC Corp
Priority to JP5963980A priority Critical patent/JPS56155437A/en
Publication of JPS56155437A publication Critical patent/JPS56155437A/en
Publication of JPS6242288B2 publication Critical patent/JPS6242288B2/ja
Granted legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M11/00—Coding in connection with keyboards or like devices, i.e. coding of the position of operated keys
    • H03M11/20—Dynamic coding, i.e. by key scanning

Landscapes

  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Input From Keyboards Or The Like (AREA)

Abstract

PURPOSE:To lower the operating voltage of a key code matrix by using a capacitor between a special code read line and a scanning line in a key code reading circuit. CONSTITUTION:Scanning lines 13-14 are scanned by decoding the output of a counter 1 with a decoder 2. When one of the keys on the key code matrix is pushed, a key signal is latched in a latch 30 via read lines 21-24 and key code read amplifiers 26-29. Also, a special code is latched in a latch 42 via the special code read line and an amplifier 41. In order to prevent the sneaking by the use of capacitors 36-40, the input impedances of amplifiers 26-29 are made sufficiently lower than the input impedance of the amplifier 41, to make the amplifiers 26-29 inactive to the sneaking signal. Hence, as compared to the prior case in which diodes are used between the special code read lines of the scanning lines, the operating voltage is made lower because there is no voltage drop by the diodes.
JP5963980A 1980-05-02 1980-05-02 Key code reading circuit Granted JPS56155437A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP5963980A JPS56155437A (en) 1980-05-02 1980-05-02 Key code reading circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP5963980A JPS56155437A (en) 1980-05-02 1980-05-02 Key code reading circuit

Publications (2)

Publication Number Publication Date
JPS56155437A true JPS56155437A (en) 1981-12-01
JPS6242288B2 JPS6242288B2 (en) 1987-09-08

Family

ID=13118987

Family Applications (1)

Application Number Title Priority Date Filing Date
JP5963980A Granted JPS56155437A (en) 1980-05-02 1980-05-02 Key code reading circuit

Country Status (1)

Country Link
JP (1) JPS56155437A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57159328A (en) * 1981-03-27 1982-10-01 Fujitsu Ltd Keyboard discriminating system
JPS585124U (en) * 1981-06-30 1983-01-13 富士通株式会社 keyboard encoder
JPS5966735A (en) * 1982-10-08 1984-04-16 Hitachi Ltd Word processor
JPS59163626A (en) * 1983-03-07 1984-09-14 Sanyo Electric Co Ltd Keyboard identifying system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57159328A (en) * 1981-03-27 1982-10-01 Fujitsu Ltd Keyboard discriminating system
JPS585124U (en) * 1981-06-30 1983-01-13 富士通株式会社 keyboard encoder
JPS5966735A (en) * 1982-10-08 1984-04-16 Hitachi Ltd Word processor
JPS59163626A (en) * 1983-03-07 1984-09-14 Sanyo Electric Co Ltd Keyboard identifying system

Also Published As

Publication number Publication date
JPS6242288B2 (en) 1987-09-08

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