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1.2. Keypad Subsystem
The keypad subsystem scans the key matrix, converts the scan code to its
associated key value, and stores the value in the input buffer of keyboard for
program utilization. Note that the [SHIFT] key is not stored into the buffer,
it is used to distinguish the alphabetic and numeric mode of associated key
position and provide an alternative key code. The following table shows the
key values of each key.
Table of Key Values
Key Value
Key Value
Key Value
Key Value
A 41H O 4FH [SP] 20H
F1/
?
?
86H
B 42H P 50H 0 30H
F2/??
87H
C 43H Q 51H 1 31H
F3/
?
?
88H
D 44H R 52H 2 32H
F4/
?
?
89H
E 45H S 53H 3 33H F5/* 8AH
F 46H T 54H 4 34H
F6/?
8BH
G 47H U 55H 5 35H
F7/?
8CH
H 48H V 56H 6 36H
I 49H W 57H 7 37H
J 4AH X 58H 8 38H
K 4BH Y 59H 9 39H
L 4CH Z 5AH [E] 0DH
M 4DH + 2BH [C] 08H
N 4EH - 2DH
.
2EH
1.3. Display Subsystem
This subsystem provides the interface functions: Display character, Display
string, Set cursor position, and Clear screen display. The display coordinates
are organized as follows:
Min Min Max Max
Row Col Row Col
0 0 1 15
The origin (0,0) is always at the upper left hand corner.