1
* This specification are subject to be changed without notice.
EM83053A/BH
KEYBOARD ENCODER
6.9.2000
GENERAL DESCRIPTION
The EM83053A/BH microcontroller is dedicated to a keyboard encoder ,specially designed for IBM PC AT and
all compatible machines. The EM83053A/BH controll all scan codes, three LEDs status, scan timing and
communications between the keyboard and PC. It is easy to implement a high performance, low cost keyboard
with the minimal external components.
FEATURES
Low cost - eliminate need external components.
Phantom key detects.
RC oscillator ( 1.8432MHz ).
Support scan code set 1 ,2 and 3.
Support PC AT and PS/2 keyboard .
Low power CMOS device technology.
Internal pull-up resistor.
Tri-state outputs for easy board application.
Built-in 4K ROM.
Support WINDOWS
TM
95, 98, 2000 keys.
104/107 keys with multi-media or other special application keyboard encoder.
WINDOWS is registered trademarks of Microsoft corperation.
APPLICATION
IBM PC AT or compatible machine keyboard.
IBM PS/2 model 30,50,60,80 or compatible machine keyboard.
Japanese keyboard.
Korean keyboard.
Brazilian keyboard.
European keyboard.
PIN ASSIGNMENTS
P91
P92
P93
P94
P95
P50
P51
P52
P53
P54
6
7
8
9
10
11
12
13
14
15
36
35
34
33
32
31
30
29
28
27
R_OSCI
VDD
CAPS
P55
P56
P57
P80
P81
P82
P83
P84
P85
P86
P87
16
17
18
19
20
21
22
23
24
25
26
5
4
3
2
1
39
38
37
NUM
SCROLL
P67
P66
P65
P64
P63
P62
P61
P60
EM83053BH
P90
CLK
DATA
OSCO
GND
P91
P92
P93
XT
P95
P50
P51
P52
P53
P54
6
7
8
9
10
11
12
13
14
15
36
35
34
33
32
31
30
29
28
27
R_OSCI
VDD
VDD
CAPS
P55
P56
P57
P80
P81
P82
P83
P84
P85
P86
P87
16
17
18
19
20
21
22
23
24
25
26
5
4
3
2
1
40
39
38
37
NUM
SCROLL
P67
P66
P65
P64
P63
P62
P61
P60
EM83053AH
P90
CLK
DATA
OSCO
GND
* This specification are subject to be changed without notice.
2
6.9.2000
EM83053A/BH
KEYBOARD ENCODER
PIN DESCRIPTIONS
Symbol
I/O
Function
P50
O
Column 3 Low output scan line, 3-state
P51
O
Column 4 Low output scan line, 3-state
P52
O
Column 5 Low output scan line, 3-state
P53
O
Column 6 Low output scan line, 3-state
P54
O
Column 7 Low output scan line, 3-state
P55
O
Column 14 Low output scan line, 3-state
P56
O
Column 13 Low output scan line, 3-state
P57
O
Column 12 Low output scan line, 3-state
P80
O
Column 11 Low output scan line, 3-state
P81
O
Column 15 Low output scan line, 3-state
P82
O
Column 10 Low output scan line, 3-state
P83
O
Column 8 Low output scan line, 3-state
P84
O
Column 9 Low output scan line, 3-state
P85
O
Column 0 Low output scan line, 3-state
P86
O
Column 16 Low output scan line, 3-state
P87
O
Column 17 Low output scan line, 3-state
P90
O
Column 1 Low output scan line, 3-state
P91
O
Column 2 Low output scan line, 3-state
VSS
I
Ground
SCROLL
O
Scroll Lock Indicator
NUM
O
NUM Lock Indicator
CAPS
O
Caps Lock Indicator
P60
I
Row 0 Input scan line, internal pull high ( 17K
)
P61
I
Row 1 Input scan line, internal pull high ( 17K
)
P62
I
Row 2 Input scan line, internal pull high ( 17K
)
P63
I
Row 3 Input scan line, internal pull high ( 17K
)
P64
I
Row 4 Input scan line, internal pull high ( 17K
)
P65
I
Row 5 Input scan line, internal pull high ( 17K
)
P66
I
Row 6 Input scan line, internal pull high ( 17K
)
P67
I
Row 7 Input scan line, internal pull high ( 17K
)
CLK
I/O
CLOCK line for IBM communication , internal pull high ( 2.2K
)
DATA
I/O
DATA line for IBM communication , internal pull high ( 2.2K
)
V
DD
I
+5V Power Supply
OSCO
O
CLOCK output
R_OSCI
I
Connect 51K OHM resistor for 1.8432 MHz oscillation
3
* This specification are subject to be changed without notice.
EM83053A/BH
KEYBOARD ENCODER
6.9.2000
FUNCTION DESCRIPTIONS
Keyboard buffer
The keyboard will buffer 16 bytes in a first-in-first-out order when the system is able to receive scan codes
from the keyboard. The response codes and repeated codes will not be buffered. If keystrokes generate a
multiple-byte sequence, the entire sequence must fit into the buffer or the keystroke is discarded and a buffer-
overrun condition occurs.
Power-on Reset and self test
The duration of the keyboard Power-on-Reset(POR) should be within 150 milliseconds and 2 seconds after
the power is applied to the keyboard.
After executing POR , the keyboard executes a self test. The LEDs are turned on at the beginning and off at
the end of the self test. The self test takes a minimum 300 milliseconds and a maximum 500 milliseconds.
If the self test is successful, a completion code AA hex is sent to the system and the keyboard starts scanning.
If the self test fails, and error code is sent, the keyboard is disabled and waits for a command from the system.
The completion codes are sent between 450 milliseconds and 2.5 seconds after POR, and between 300 and
500 milliseconds after a RESET command is acknowledged.
Keyboard data output
When the keyboard is ready to send data to the system, it first checks clock and data lines. If either one is in
the low state, data is stored in the keyboard buffer. If both are in the high state, keyboard starts clocking data
out. Data will be valid before the trailing edge and after the leading edge of the clock pulse. During the
transmission the keyboard checks the clock line at least every 60 microseconds . If the system lowers the clock
lines before the leading edge of the 10th clock, the keyboard should stop sending, then buffer the data and
return clock and data lines to high state.
Keyboard data input
When the system is ready to send data to the keyboard, it first checks clock line to see if keyboard is sending
data. If keyboard is not sending data or it is sending data but has not reached the 10th clock, the system can
inhibit the interface by forcing the clock line low for more than 60 microseconds and prepares to send data.
The keyboard checks clock line status at least every 5 milliseconds. If a system Request to Send(RTS) is
detected, the keyboard clocks 11 bits in. After the 10th bit, the keyboard checks for a high state in data line
then pulls it low and clocks one more bit to signal the system that data has been received. If data is low after
the 10th bit, it indicates a frame error. The keyboard should continue to count until data line goes high, then
pulls it low and issues a RESEND to the system.
Command from the system
The system can send commands to the keyboard at any time. The keyboard needs to respond within 20
milliseconds, unless the system prevents keyboard output, when doing self test or executing a RESET.
The following are the keyboard input commands and the actions that keyboard needs to take.
Set /Reset Status indicators ( Hex ED )
- Responds ACK.
- Receives option byte.
* This specification are subject to be changed without notice.
4
6.9.2000
EM83053A/BH
KEYBOARD ENCODER
- Responds ACK.
- Updates status indicators.
- Returns to previous scanning state.
Echo ( Hex EEH )
- Responds with EE hex.
- Returns to previous scanning state.
Invalid commands ( Hex EF and F1 )
- Returns a RESEND command.
- Returns to previous scanning state.
Select Alternate Scan Codes ( Hex F0 )
- Responds ACK.
- Clears output buffer.
- Sets the default typematic rate/delay.
- Clears last typematic key.
- Receives option byte.
- Responds ACK.
- Option byte =
01 : selects scan code set 1
02 : selects scan code set 2
03 : selects scan code set 3
- Returns to previous scanning rate.
Read ID (F2)
- Responds with ACK.
- Discontinues scanning.
- Sends two ID bytes. The second byte will be sent within 500 uS after first byte.
- Resumes scanning.
Set Typematic Rate/Delay ( Hex F3 )
- Responds ACK.
- Receives rate/delay value byte
- Responds ACK.
- Set rate/delay (* Note 1)
- Returns to previous scanning state.
* Note 1
1. Repeat period = ( 8+A ) x ( 2B) x 0.00417 seconds
A : binary value of bits 2, 1, and 0.
B : binary value of bits 4 and 3.
2. Delay = ( C +1 ) x 250 milliseconds
C : binary value of bits 6 and 5. Bit 7 is always 0.
5
* This specification are subject to be changed without notice.
EM83053A/BH
KEYBOARD ENCODER
6.9.2000
bit 4~ bit 0
typematic rate
20%
bit 4~ bit 0
typematic rate
20%
00000
30.0
10000
7.5
00001
26.7
10001
6.7
00010
24.0
10010
6.0
00011
21.8
10011
5.5
00100
20.0
10100
5.0
00101
18.5
10101
4.6
00110
17.1
10110
4.3
00111
16.0
10111
4.0
01000
15.0
11000
3.7
01001
13.3
11001
3.3
01010
12.0
11010
3.0
01011
10.9
11011
2.7
01100
10.0
11100
2.5
01101
9.2
11101
2.3
01110
8.6
11110
2.1
01111
8.0
11111
2.0
3. Default rate = 10.9 chars/sec + 20%
Default delay = 500 mS
20%
Enable ( Hex F4 )
- Responds with ACK.
- Clears output buffer.
- Clears last typematic key.
- Start scanning.
Default Disable (Hex F5)
- Responds with ACK.
- Resets all conditions to power-on state.
- Clears output buffer.
- Sets the default key type ( scan code set 3 only ).
- Set the default typematic rate/delay.
- Clears last typematic key.
- Stops scanning,
Set Default (Hex F6 )
- Responds with ACK.
- Resets all conditions to power-on state.
- Clears output buffer.
- Sets the default key type ( scan code set 3 only ).
- Set the default typematic rate/delay.
- Clears last typematic key.
- Continues scanning,
Set All Keys ( Hex F7,F8,F9,FA )
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