(8,\92
BYTE
MASK
Rom)
(5v)
V.-C
A9
A9
Aszgmo
Arr
D1
D6
D5
D4
D3
& @BE B
BBEBB BEBN
I
Ar
As
A5
A4
A3
A2
An
Ao
Do
Du
Oz GND
A.»~Aw-»
Address
Bus
m~D~-
Data
Bus
_
----- ChipSelect
-----
Chip
Select
Fig.
5-6
PD2364C
is
SK
Byte
Mask
Rom
(Read
Only
Memory)
_
The
System
Program
is
written
in
this
ROM.
I3
8
192
B
te
is
selected
by
13
address
line
1.
The
Memory
Address
of
2
=
,
y
(AO-Al2)
.
2.
The
content
of
the
Memory
is
outputted
by
8
lines
of
data
line
(DO-D7)
3.
Chip
Select
(EE)
is
Low
active
and
content
of
the
memory
is
outputted
to
data
line
.
Basic
and
Monitor
System
Program
is
written
in
three
pieces
of
ROM
(uPD2364C-331,
pPD2363C-332)
in
MB-6890.
The
Address
is
allocated
by
ROM
Address
decoder
as
shown
table
5-2.
TABLE
5-2
R OM
I
Address
/1PD2se4c-aao
|
$
A oo o
~
s
BFFF
,,PDz3e4c-331
1
s
c ooo
~
s
n1=z=1=
i
»~
v-
~
-
-
A
--Q-QQ
u P D 2 3 6 4 C 3 3 2
L
"UU
5
bb"
s
FFF
o
~
s
FFFF
The
block
diagram
of
the
ROM
is
shown
at
Fiq
5-7.
212
Output
M2
Buffer
A0
->
3
1
A»
o-Ag
_.Q
YY
Selector
A2
o-+3
-.
3.
A5
o-_~$
_.L_f1D_
_______
CS
M
Q_..H
_.r-’
PrOqra;r
A5
S33
_>
A6
fi
E;
Memory
A
AT
m
3
CS
Aao->C.’
_>O’
(8,l92>
A9
_.’S2
__
E1
5
P W C
.. O_.2
,Q
Buffer
\
A||;¢-L
i.._..¥
¥7§~
E
-1
Summary of Contents for MB-6890
Page 1: ...HITACHI PERSONAL COMPUTER MB 6890 SERVICE MANUAL I R 0 3012 98 ...
Page 2: ...HITACHI PERSONAL COMPUTER MB 6890 SERVICE MANUAL ev O 30 1 2 1 ...
Page 42: ... one of page 40 44 missing ...
Page 122: ......
Page 123: ......
