DAZZLER =-
=_-::.
---
_-::.
=-=
===
_
___________
~=-==
=====E:===-===
--
---------
also be turned off manually
by
depressing
the
"clear"
sNitch on the computer
front
panel. The
remaining seven bits
of
output
port
0EH are used
to
set
the
starting location
of
the
picture
to
be display-
ed in the
computer's
memory. As will be discussed
below,
the picture may require
512
bytes
of
mem-
ory
or
21<
bytes
of
memory
depending on
the
mode
in
which
the
DAZZLER®
is
operating.
In
any
event,
this
must be static
memory
with
an
access
time
of
,microsecond
or
faster. Asummary
of
the
use
of
outpa!
port 0EH
is
shown
below.
Bit
07
is
not
used. Bit
06
is
used
to
set
normal."
resolution (32 x
32
element
picture
tor
512
bytes
or
_
64
x
64
element
picture
tor
2K bytes)
or
resolution
X 4 (64 x
64
element
picture for 512
bytes
or
128
x128
element
picture
tor
2K
bytes). Bit
05
sets
the
amount
of
computer
memory (starting
at
the
loca-
tion
given
to
output
port
0EH) allocated
to
the pic-
ture. When
D5
is
"1,"
2K bytes
of
memory
are used.
When
05
is
"0,"
512
bytes
are
used. Bit D4
is
used
to
select between a·black·and-white display and a
color display. Bits
03-00
are used
in
resolution X 4
mode
to
set
the
color
of
a
color
picture
or
the
inten-
sity
of
ablack-and-white picture. Bits
03-00
are
not
used
in
normal resolution mode.
~
'(ro.'
,;;t
'-/.""
-,...
~
..
'
_I
\i
••
~
,~
->
- , •
~
MSB
LSB
Only
two
bits
of
input
port
0EH are used. Bit
07
is
low during
odd
lines and high during even
lines. Bit D6 goes low for 4
ms
between frames
to
indicate
end
of
frame
.
,
_07~
~
'.T:-
c1)..!'t.
_".h'l:tj:'
'O','
1,'.:
~,\1'
,a)-
-f:i,Q;l]o
~.~
--
--,-_.~
-
._"-~"
STARTING
ADDRESS
OF
PICTURE
Output
Port
DEH
Output
port
0FH
is
used
to
set
the
format
of
the
TV picture.
The
function of each
of
the
eight
bits
of
this
output
port
is
shown
in
this table:
07
_
Not
u>ed.
06~1
_
R.""lu,ion
X4.
calo.
~nd
intensity
..
t
by
D4
to
DO,
D6~O
_
No'm~1
....
olulion_
(32)(32
for
S12·byte
plctuo
•.
64X&4
10'
2~·by,0
p;cluro.)
Color
and
inlonsity
of
each
pi<1u"
ol.m'nt
..
I
by
4·bit
wo.d.
,n
Ihe
OOmout.r
momof)'.
05~t
_
Pi"tu,"
In
2K
bY'e>
01
memo'y.
D4~O
-f11.ck-and-Whlto
pictu,o.
~
D4~1
-
Colo.
p'CIU
••.
---,,-
~
r~
"
D3~1
_
Hiih
intons.ly
colo..
In
,,,,,,Iulien
)(
4
black-
and-whit.
mod
••
D3 is
II
••
D3~O
-
Lcw
i"'.mily
colo..
mD,to;Qn,licant
bit
of
4-bit
;nt.n.ity
etm1to(
D2~1
-
BI""
,,"o<d.
Dlet-Gleon
Bit
DO
iotho
10'"
DO~O
_
N<,
ted
,ipniliconl
bil_
Output
Port
OFH
4
1
Only
Two
8its
of
Inpur
Port
Jr~
U.ed. j•
'---------
In
order
to
generate
aTV picture
with
OAZ-
ZLER®,
the
information
that
the DAZZLER(;)
reads
from
the
computer
memory
must
be
properly
formatted.
In
resolution X 4 mode, each point
all
the
TV screen
is
controlled
by
just
one
bit
in
the
computer
memory. When
that
bit
is
a
"1"
the cor-
responding element
of
the
picture
is
on. When
that
bit
is
a</0" the
picture
element
is
off.
In
resolution
X 4
mode,
the
color
and intensity of
the
picture
is
set by
bits
00
to
03
of
the control
word
at
output
port
0FH.
For full color
in
resolution X 4 mode,
multiple frames
of
different colors
must
be
intel--
leaved.
In
norma! resolution mode,
the
color and inten-
sity
of
each
element
of
the TV picture are
contra
-
led by afour-bit
"nybble"
in
the
computer
memory.
Two
elements
of
the
picture
are
thus
stored
in
eacn
byte (8 bits) of memory. (For this reason, a64 x
64
picture in normal resolution
mode
requires
2K
of
memory.)
The
lowest order
bit
of
each nybble
(00)
•
determines
whether the corresponding element
of
::
the
picture
contains red
(1)
or
no
red
{0l. Similarly,
D1
controls
green,
02
controls blue,
and
D3
sets
