Download Master Service Manual

Master Series
Service Manual
nKBEN:- Generated by the system VIA, this line is taken active low to enable the row and column
addresses to be determined by the Operating System.
MHz1:- This is the timing reference,
SWT1, RSTO:- These connections are not used.
The Keyboard Matrix
The keys are physically arranged as a QWERTY type keyboard with 1O function keys, 4 cursor control
keys and a 19 key numeric keypad.
The matrix is as follows:-
RO
C0 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12
ESC f1 f2 f3 f5 f6 f8 f9 I @ 4' 5'
2’
R1
TAB Z
sp V
B M
,
.
R2
SHIFT S
LOCK
C
G
H
N
L
; ]
R3
X
F
Y
J
K
@
R4
CAPS A
LOCK
!
“
1
2
R5
f0
W
D
E
#
3
R6
Q
R7
SHIFT CTRL
R
T
$
4
7
%
5
&
U
6
I
f4 8
O
,
9
< >
/ copy 0'
1’
3’
+ }
del #'
*’
,’
: ret
P
[
-
*
del'
{
+’
@
)
0 _ @
(
f7
/'
8'
=
^ @
£
.’
-’ ret’
9'
~
6' 7'
Figure 5
Sound Generator
The sound generator is an SN7694A device, Three sound channels plus one pseudo random noise
channel are provided. The full description of it is found in the manufacturers data sheet. It is provided
with a reference clock of 4MHz from central timing. The output is filtered as described in the section
'Audio Circuitry' .
The output can also be connected by screened cable to the optional modem.
This output is mixed on the modem board to generate dialling tones for DTMF exchanges where the
modem hardware does not provide such tones itself.
20 Issue 1
20
Issue 1