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PDF K25C81-FB Data sheet ( Hoja de datos )

Número de pieza K25C81-FB
Descripción Versatile PC/XC/AT/PS/2 Compatible Keyboard Encoder
Fabricantes Semtech 
Logotipo Semtech Logotipo



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FlexiCoderTM K25C81
Versatile PC/XC/AT/PS/2 Compatible
Keyboard Encoder
HID & SYSTEM MANAGEMENT PRODUCTS, KEYCODERTM FAMILY
DESCRIPTION
The FlexiCoderTM is a versatile, low-
power keyboard encoder. It offers
two bi-directional channels for
communicating with a
PC/XT/AT/PS2 system, and/or any
optional keyboard-compatible
devices, such as an 83 or 101/102
standard desktop keyboard, OCR,
barcode reader, etc. The K25C81
directly interfaces a PC keyboard
port, making custom keyboard to
system communications fully
transparent.
On an 8 x 18 matrix, the
FlexiCoderTM will scan, debounce
and encode up to 144 keys. Scan
codes corresponding to single keys
of the IBM 101 keyboard, or a
combination of these keys when
depressed with Shift, Ctrl, and Alt
keys, are generated with each key
press. Custom keypad input is not
effected by the Shift States of an
external keyboard.
Users can conveniently define key
assignments on the matrix as single
or repeating actions. All keys must
be released between key strokes or
scanning is suspended. The
encoder can buffer up to 122
keycodes, and control inputs and
outputs are provided for interfacing
with contact keyboards.
The FlexiCoderTM is ideal for use
with either BIOS-compatible chip
sets or single-board computers for
PC systems requiring a custom
keyboard / keypad as an alternate
or additional input device. Boards
and evaluation kits are immediately
obtainable and ready to connect.
FEATURES
• Directly interfaces a PC
keyboard port
• Encodes up to 144 custom keys
on an 8 X 18 matrix
• Buffers up to 122 keycodes
• Interfaces to 83/101/102
standard keyboard or other
8042-compatible device
APPLICATIONS
• Custom keyboards/keypads
• Control panels
• Automatic teller machines
• Embedded control systems
• Public Information Kiosks
PIN ASSIGNMENTS
• Enables custom keypad scan
codes to remain unaffected by
the Shift States of an external
keyboard
• Includes jumper-selectable auto-
repeat for designated keys
• Offers two-key inhibit scanning
mode
• Instrumentation
• Test and Measurement equipment
• Point of Sales terminals
• Industrial Controllers
• Medical Instruments
_RESET 1
_IRQ 2
VX 3
C17 4
R6 5
RP 6
KD 7
KC 8
EKC 9
EKD 10
C16 11
C0 12
C1 13
C2 14
C3 15
C4 16
C5 17
C6 18
C7 19
Vss 20
DIP
40 Vcc
39 OSCI
38 OSCO
37 EKC1
36 R7
35 NC
34 R5
33 R4
32 R3
31 R2
30 R1
29 R0
28 C8
27 C9
RP
KD
KC
EKC
EKD
C16
C0
C1
C2
C3
C4
6
7
12
17
18
26 C10
25 C11
24 C12
23 C13
22 C14
21 C15
1
PLCC
23
40
39 R7
NC
R5
R4
R3
34 R2
R1
R0
C8
C9
29 C10
28
R6
RP
KD
KC
EKC
EKD
C16
C0
C1
C2
C3
1
QFP
NC
R5
R4
R3
R2
R1
R0
C8
C9
C10
C11
FlexiCoderTM is a trademark of Semtech Corp. All
other trademarks belong to their respective
companies.
Copyright Semtech, 1997-2001
DOC5-C81-DS-105
1
www.semtech.com

1 page




K25C81-FB pdf
EXT. KBD COMMUNICATION
The external keyboard
communication port of the
FlexiCoderTM fully emulates a
standard 8042, available to an
83/101/102 external keyboard or
other compatible device.
Communication with an external
keyboard is accomplished via EKC
and EKD, Clock and Data lines
respectively. A third pin, EKC1
which connects to the Clock Line,
interrupts the controller whenever
an external keyboard initiates a
communication.
When power is first applied, the
controller proceeds with the
standard reset sequence with the
external keyboard. Data and
commands coming from the
external keyboard are buffered in
the controller’s FIFO, along with
data from the scanned matrix, and
then presented to the system as if
originating from a single source.
Commands and data from the
system, after being acknowledged,
are then transmitted to the external
keyboard.
MODE CONTROL
The FlexiCoderTM implements all the
standard functions of
communication with a BIOS-
compatible PC/XT or AT/PS/2 host
system. Two lines, KC and KD,
provide bi-directional clock and
data signals according to the
protocol (PC or AT) selected. In
addition, the K25C81 supports
commands from and to the system,
as described in the IBM Technical
Reference Manuals. The following
table shows the commands that the
system may send and their value in
hex.
Command
Hex Value
Set/Reset Status
Indicators
ED
Echo
EE
Invalid Command
EF
Select Alternate
Scan Codes
F0
Invalid Command
F1
Read ID
F2
Set Typematic
Rate/Delay
F3
Enable
F4
Default Disable
F5
Set Default
F6
Set All Keys
Typematic
Make/Break
Make
Typematic/Make/Break
F7
F8
F9
FA
Set Key Type
Typematic
Make/Break
Make
FB
FC
FD
Resend
FE
Reset
FF
Table 2: Keyboard Commands from the
System (AT/PS/2 protocol)
These commands are supported in
the AT/PS/2 protocol and can be
sent to the keyboard at any time.
Mode 1 accepts only the ‘reset’
command. Commands shown in
italics do not affect the operation of
the K25C81. Nevertheless, they
are acknowledged and relayed to
the external keyboard, if an
external standard keyboard is
present.
The following table shows the
commands that the keyboard may
send to the system.
Command
Hex Value
Key Detection
Error/Overrun
00*
Keyboard ID
83AB
BAT Completion Code
AA
BAT Failure Code
FC
Echo
EE
Acknowledge (Ack)
FA
Resend
FE
Key Detection
Error/Overrun
FF*
*Scan Code Set 2
Table 3: Keyboard Commands to the
System (AT/PS/2 protocol)
When an external keyboard is
connected, commands from the
system will also be directed to the
external keyboard. Presence or
absence of an external keyboard
will not affect the normal operation
of the FlexiCoderTM.
Copyright Semtech, 1997-2001
DOC5-C81-DS-105
5
www.semtech.com

5 Page





K25C81-FB arduino
ELECTRICAL SPECIFICATIONS
Absolute Maximum Ratings
Ratings
Supply Voltage
Input Voltage
Current Drain per Pin
(not including Vss or Vdd)
Operating Temperature
K25C81
Storage Temperature Range
Symbol
Vdd
Vin
I
Ta
Tstg
Value
-0.3 to +7.0
Vss -0.3 to Vdd +0.3
25
T low to T high
40 to +85
-65 to +150
Unit
V
V
mA
°C
°C
Thermal Characteristics
Characteristic
Symbol
Value
Unit
Thermal Resistence
Tja
° C per W
Plastic
60
DIP -60
Plcc 70
DC Electrical Characteristics (Vdd=5.0 Vdc +/-10%, Vss=0 Vdc, Temperature range=T low to T high unless otherwise noted)
Characteristic
Symbol
Min
Typ
Max
Unit
Output Voltage (I load<10µA)
Vol
0.1 V
Voh Vdd0.1
Output High Voltage (I load=0.8mA) Voh
Vdd0.8
V
Output Low Voltage (I load=1.6mA) Vol:
0.4 V
Input High Voltage
Vih
0.7xVdd
Vdd V
Input Low Voltage
Vil
Vss
0.2xVdd
V
Supply Current
Idd
4.7 7.0 mA
I/O Ports Hi-Z Leakage Current
Iil
+/-10
µA
Input Current
Iin
+/- 1
µA
I/O Port Capacitance
Cio
8 12 pF
Control Timing (Vdd=5.0 Vdc +/-10%, Vss=0 Vdc, Temperature range=T low to T high unless otherwise noted)
Characteristic
Symbol
Min
Max
Frequency of Operation
fosc
Crystal Option
4.0
External Clock Option
dc 4.0
Unit
MHz
Copyright Semtech, 1997-2001
DOC5-C81-DS-105
11
www.semtech.com

11 Page







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