Sharp MZ-80B - Page 61

54
The relationship between strobe signals and bit da ta during keyboard scan is shown in Table 4.5.
Strobe signals are delivered
to four terminals (A
3
,
A
2
, A
1
,
A
0
) ,
fed into demultiplexer 154, th en
deli
ve red to 12 keyboard strobe input termina ls. Keys are discriminated by strobe si gnals and key
data.
For instance, when the strobe is '6H' and the key dat a is ' F7H ', it indicates that the 'S' key is
being pressed.
Table 4.5 Key scanni ng strobe si gna ls and bit da ta
E MOD E 0
1 2 3 4 5 6 7
~
F I
F2
F3 F4
Fs
F6
F7 Fs
0
0
F9 F IO
8
9
00
•
+
-
1
1
0
1 2 3
4
5
6 7 2
1
TAB
SPACE
i cR i
[!]
ITJ
G G
I BREAK I
3
+-
a
b c
d
e
f g
I
f--
A
~
B
f--
c
f--
D
T
E
:r
F
f--
G
R=
4
2
-+
•
•
f--
H
h
I
i
J
j
K
k
I
M
m n
0
nr ~
f--
~
L
iF
-
N f-- 0
PI=
5
3
F=
£ 0
p
p
Q
q
R
r
s
s
T
t
u
u
v
v
w
f-- i--
11=
p-
I
;r
f--
w
f--
6
3
hr r
•
h
X
y
z
-
\
I
t
>
<
X
,.-
y
f--
z
~
A
f-;:-
-
?
-
f-- f--
7
r-r
\
.!,
'
¥
1T
-
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#
$
%
&
0
1 2 3 4
5 6
7 8
4
(
)
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+
=
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I
2
8 9
@
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l
9
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-
}
~
CLR
......1
INST
l
;:;;;
(.i1
A
0
5
:r:
Q
SPCL GRPH
ISFT LOCK
SHIFT RVS B