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MicroBlaze Development Kit Spartan-3E 1600 Edition User Guide 65
UG257 (v1.1) December 5, 2007 www.xilinx.com
Keyboard
R
Some keys, called extended keys, send an “E0” ahead of the scan code and furthermore,
they might send more than one scan code. When an extended key is released, an “E0 F0”
key-up code is sent, followed by the scan code.
The host can also send commands and data to the keyboard. Table 8-3 provides a short list
of some often-used commands.
The keyboard sends commands or data to the host only when both the data and clock lines
are High, the Idle state.
Because the host is the bus master, the keyboard checks whether the host is sending data
before driving the bus. The clock line can be used as a clear to send signal. If the host pulls
the clock line Low, the keyboard must not send any data until the clock is released.
Figure 8-3: PS/2 Keyboard Scan Codes
ESC
76
` ~
0E
TA B
0D
Caps Lock
58
Shift
12
Ctrl
14
1 !
16
2 @
1E
3 #
26
4 $
25
5 %
2E
Q
15
W
1D
E
24
R
2D
T
2C
A
1C
S
1B
D
23
F
2B
G
34
Z
1Z
X
22
C
21
V
2A
B
32
6 ^
36
7 &
3D
8 *
3E
9 (
46
0 )
45
- _
4E
= +
55
Back Space
66
Y
35
U
3C
I
43
O
44
P
4D
[ {
54
] }
5B
\ |
5D
H
33
J
3B
K
42
L
4B
; :
4C
' "
52
Enter
5A
N
31
M
3A
, <
41
> .
49
/ ?
4A
Shift
59
Alt
11
Space
29
Alt
E0 11
Ctrl
E0 14
F1
05
F2
06
F3
04
F4
0C
F5
03
F6
0B
F7
83
F8
0A
F9
01
F10
09
F11
78
F12
07
E0 75
E0 74
E0 6B
E0 72
UG257_08_03_060506
Table 8- 3: Common PS/2 Keyboard Commands
Command Description
ED Tu r n on / of f N u m L o c k, C ap s Lo c k , a nd S c ro l l L o c k L E Ds . The keyboard
acknowledges receipt of an “ED” command by replying with an “FA”, after
which the host sends another byte to set LED status. The bit positions for the
keyboard LEDs are shown below. Write a ‘1’ to the specific bit to illuminate the
associated keyboard LED.
EE Echo. Upon receiving an echo command, the keyboard replies with the same scan
code “EE”.
F3 Set scan code repeat rate. The keyboard acknowledges receipt of an “F3” by
returning an “FA”, after which the host sends a second byte to set the repeat rate.
FE Resend. Upon receiving a resend command, the keyboard resends the last scan
code sent.
FF Reset. Resets the keyboard.
76543210
Ignored
Caps
Lock
Num
Lock
Scroll
Lock