поискавой системы для электроныых деталей
  Russian  ▼
ALLDATASHEETRU.COM

X  

74C922 датащи(PDF) 6 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
номер детали 74C922
подробное описание детали  16, 20-Key Encoder
Download  10 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
производитель  NSC [National Semiconductor (TI)]
домашняя страница  http://www.national.com
Logo NSC - National Semiconductor (TI)

74C922 датащи(HTML) 6 Page - National Semiconductor (TI)

Back Button 74C922 Datasheet HTML 2Page - National Semiconductor (TI) 74C922 Datasheet HTML 3Page - National Semiconductor (TI) 74C922 Datasheet HTML 4Page - National Semiconductor (TI) 74C922 Datasheet HTML 5Page - National Semiconductor (TI) 74C922 Datasheet HTML 6Page - National Semiconductor (TI) 74C922 Datasheet HTML 7Page - National Semiconductor (TI) 74C922 Datasheet HTML 8Page - National Semiconductor (TI) 74C922 Datasheet HTML 9Page - National Semiconductor (TI) 74C922 Datasheet HTML 10Page - National Semiconductor (TI)  
Zoom Inzoom in Zoom Outzoom out
 6 / 10 page
background image
Typical Applications (Continued)
Asynchronous Data Entry Onto Bus (MM74C922)
TLF6037 – 12
Outputs are in TRI-STATE until key is pressed then data is placed on bus
When key is released outputs return to TRI-STATE
Expansion to 32 Key Encoder (MM74C922)
TLF6037 – 13
Theory of Operation
The MM74C922MM74C923 Keyboard Encoders imple-
ment all the logic necessary to interface a 16 or 20 SPST
key switch matrix to a digital system The encoder will con-
vert
a
key
switch
closer
to
a
4(MM74C922)
or
5(MM74C923) bit nibble The designer can control both the
keyboard scan rate and the key debounce period by altering
the oscillator capacitor COSE and the key bounce mask
capacitor CMSK Thus the MM74C922MM74C923’s per-
formance can be optimized for many keyboards
The keyboard encoders connect to a switch matrix that is 4
rows by 4 columns (MM74C922) or 5 rows by 4 columns
(MM74C923) When no keys are depressed the row inputs
are pulled high by internal pull-ups and the column outputs
sequentially output a logic ‘‘0’’ These outputs are open
drain and are therefore low for 25% of the time and other-
wise off The column scan rate is controlled by the oscillator
input which consists of a Schmitt trigger oscillator a 2-bit
counter and a 2 – 4-bit decoder
When a key is depressed key 0 for example nothing will
happen when the X1 input is off since Y1 will remain high
When the X1 column is scanned X1 goes low and Y1 will go
low This disables the counter and keeps X1 low Y1 going
low also initiates the key bounce circuit timing and locks out
the other Y inputs The key code to be output is a combina-
tion of the frozen counter value and the decoded Y inputs
Once the key bounce circuit times out the data is latched
and the Data Available (DAV) output goes high
If during the key closure the switch bounces Y1 input will
go high again restarting the scan and resetting the key
bounce circuitry The key may bounce several times but as
soon as the switch stays low for a debounce period the
closure is assumed valid and the data is latched
A key may also bounce when it is released To ensure that
the encoder does not recognize this bounce as another key
closure the debounce circuit must time out before another
closure is recognized
The two-key roll-over feature can be illustrated by assuming
a key is depressed and then a second key is depressed
Since all scanning has stopped and all other Y inputs are
disabled the second key is not recognized until the first key
is lifted and the key bounce circuitry has reset
The output latches feed TRI-STATE which is enabled when
the Output Enable (OE) input is taken low
6


Аналогичный номер детали - 74C922

производительномер деталидатащиподробное описание детали
logo
Fairchild Semiconductor
74C922 FAIRCHILD-74C922 Datasheet
114Kb / 10P
   16-Key Encoder 20-Key Encoder
logo
ABCircuits
74C922-SO ABCIRCUITS-74C922-SO Datasheet
122Kb / 5P
   Keyboard / Keypad Encoder for up to 16 switches
December 2012
More results

Аналогичное описание - 74C922

производительномер деталидатащиподробное описание детали
logo
Fairchild Semiconductor
MM74C922WMX FAIRCHILD-MM74C922WMX Datasheet
131Kb / 11P
   16-Key Encoder 20-Key Encoder
MM74C923WMX FAIRCHILD-MM74C923WMX Datasheet
131Kb / 11P
   16-Key Encoder ??20-Key Encoder
MM74C922 FAIRCHILD-MM74C922 Datasheet
114Kb / 10P
   16-Key Encoder 20-Key Encoder
logo
Rohm
BU1851GUW ROHM-BU1851GUW Datasheet
290Kb / 13P
   GPIO ICs Series Key Encoder IC
logo
Texas Instruments
TMS5001NL TI-TMS5001NL Datasheet
401Kb / 6P
[Old version datasheet]   4-MODE DYNAMIC 90-KEY KEYBOARD ENCODER
logo
Shenzhen Huazhimei Semi...
HM2241 HMSEMI-HM2241 Datasheet
432Kb / 14P
   2-key 1 encoder capacitive touch chip
logo
IC-Haus GmbH
IC-LNG ICHAUS-IC-LNG_14 Datasheet
1Mb / 30P
   16-BIT OPTO ENCODER
logo
Bourns Electronic Solut...
PEC16-4020F-S0012 BOURNS-PEC16-4020F-S0012_15 Datasheet
368Kb / 3P
   16 mm Incremental Encoder
PEC16 BOURNS-PEC16 Datasheet
281Kb / 3P
   16 mm Incremental Encoder
PEC16 BOURNS-PEC16_13 Datasheet
359Kb / 3P
   16 mm Incremental Encoder
More results


Html Pages

1 2 3 4 5 6 7 8 9 10


датащи скачать

Go To PDF Page


ссылки URL




Конфиденциальность
ALLDATASHEETRU.COM
Вашему бизинису помогли Аллдатащит?  [ DONATE ] 

Что такое Аллдатащит   |   реклама   |   контакт   |   Конфиденциальность   |   обмен ссыками   |   поиск по производителю
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com