JPS6461813A - Key matrix switching circuit - Google Patents

Key matrix switching circuit

Info

Publication number
JPS6461813A
JPS6461813A JP62219405A JP21940587A JPS6461813A JP S6461813 A JPS6461813 A JP S6461813A JP 62219405 A JP62219405 A JP 62219405A JP 21940587 A JP21940587 A JP 21940587A JP S6461813 A JPS6461813 A JP S6461813A
Authority
JP
Japan
Prior art keywords
key
interruption
inputs
input
sources
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.)
Pending
Application number
JP62219405A
Other languages
Japanese (ja)
Inventor
Toshio Enomoto
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
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 filed Critical NEC Corp
Priority to JP62219405A priority Critical patent/JPS6461813A/en
Publication of JPS6461813A publication Critical patent/JPS6461813A/en
Pending legal-status Critical Current

Links

Abstract

PURPOSE:To eliminate the key scanning actions in a key input holding state by producing an interruption request when a key input signal has a change and inhibiting the change of the key scanning signal when all key matrix switches are kept turned off. CONSTITUTION:The key sources 3-6 are kept at high levels in a key input holding state. When all key switches are key turned off, the key inputs 31-34 are set at low levels by the pull-down resistances 27-30 with the key sources and the key inputs kept static. At the same time, a key input latch 36 and its input are also static so that no interruption is produced. When one of key switches is turned on, one of inputs 31-34 is set at a high level. Then an interruption generating circuit 35 activates an interruption request signal line 37 and applies an interruption to a CPU. The CPU judges the priority degrees and sets successively the sources 3-6 at high levels when the due conditions are satisfied to latch the states of inputs 31-34 via a latch circuit 36. These latches states are read via an input data bus 38. Thus the key scanning actions can be eliminated in a key input holding state.
JP62219405A 1987-09-01 1987-09-01 Key matrix switching circuit Pending JPS6461813A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP62219405A JPS6461813A (en) 1987-09-01 1987-09-01 Key matrix switching circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP62219405A JPS6461813A (en) 1987-09-01 1987-09-01 Key matrix switching circuit

Publications (1)

Publication Number Publication Date
JPS6461813A true JPS6461813A (en) 1989-03-08

Family

ID=16734892

Family Applications (1)

Application Number Title Priority Date Filing Date
JP62219405A Pending JPS6461813A (en) 1987-09-01 1987-09-01 Key matrix switching circuit

Country Status (1)

Country Link
JP (1) JPS6461813A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0421019A (en) * 1990-05-14 1992-01-24 Tamura Electric Works Ltd Key detecting method
JPH0540928U (en) * 1991-10-25 1993-06-01 株式会社東芝 Key input detection device
JP2011164728A (en) * 2010-02-05 2011-08-25 Yokogawa Electric Corp Touch panel device

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5250628A (en) * 1975-10-22 1977-04-22 Fujitsu Ltd Key input reading system

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5250628A (en) * 1975-10-22 1977-04-22 Fujitsu Ltd Key input reading system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0421019A (en) * 1990-05-14 1992-01-24 Tamura Electric Works Ltd Key detecting method
JPH0540928U (en) * 1991-10-25 1993-06-01 株式会社東芝 Key input detection device
JP2011164728A (en) * 2010-02-05 2011-08-25 Yokogawa Electric Corp Touch panel device

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