Advertisement
:t
:.~ ;:.~
? 0
Pl'
()c<:·~!:)so"{'
Mod u
l~:~
1.
3;:~;:!
0 -91 () 0'7
/;;~
1
R~~
v
J AN·-· 0
4·-·8~~
3.3.4
After being stretched,
the dot
streaM is gated
through Ul10 where it
picks up the underline enhanceMent and
then is sent to the enhanceMent
Multiplexor where the reMaining enhanceMents are
added
before sending
the inforMation to the analog sweep circuitry.
EnhanceMent Display
A one-to-one correspondence
exists between each byte of character data
and
each byte of
enhanceMent data held in
reCirculating line buffers
U39 and U28 respectively.
As a byte
of character data is sent to the
character
ROM
its
corresponding
enhanceMent
byte
is sent
to
the
(:~\n
han
c:
E~("'(7~n
t
~:;(~~c
t
ion wh
f.~r' (~
:i.
t
:i.
~:;
d
0~C: 0
d
f.~d
iii
n d
7'
(-?c
0
,..\b :i. n ed w:i. t
h
t h
f.~
d (}
t
5
t t,
f:-~ i:\ M
:i.
nth
f:~
~:o
n
h
i:\
n c
t=~ M 0:0
n
t
M U
1
t i
~)
1
f~ X 0
l',
U
~:?
1.
1. .
Of the
eight available bits
in the enhanceMent byte,
only
seven are
u
<.:~ (~:o
d .
F
0 U 7'
0
f
t
h
f:-~ ~:; f.-~
>
EN 0 ····E N
~3
>
s;
£.~
1
f.~
c:
t
the
b:l.:i.
n
1< >
i
n v e
f'
s
f.~
>
U
n
d
f..:O"{'
1.
i
n
(~~
and
halfhright attributes which May be selected
in
any COMbination.
Bit
EN 4
:i. s
t
h
~~
~::. f.'~
t
(~!
n
han
c
f.~
M (7:'
n
t
b :i.
t
w
h
i
c: h ,
w
h
~~
n h i q h ,
c: a
lJ
s;
£.~ £;
·t
h
~:-~
cur
r
f.~
n
t
enhanceMent to be latched
and held until another enhanceMent is set or
until the end of the current row.
Bit
ENS
is the end-of-line bit which
causes the display to be
frOM the current
character to the end of the
l' () W .
I
nth
i
~:;
way
>
t ()
C
1
f.-~
iH'
the
d
i
<.::.
p
1.
a y ,
end ....
0
f ..
··1
:i.
rH?
:i.
s
~~
e tin
the
f
:i.
r'
~:~
t
chi:) r'a c t
<-:·~r'
po s t ion ()
f
(:~a
c
h
r () w .
H
:i.
t
EN6
as
d
(-?SC
r :i. b
(~d
a
b ()
ve
of
0
r MS
t
h
(.~
M 0 S
t
s :i. q n :i.
fie ant
add r'
~~
s
~:~
bit
f
0 l'
a n B I( b Y
t
e c: h
i:) f'
act
f.~ l'
R () M .
As a character is latched into U31.0,
six of the seven enhanceMent bits
a
l' (~:o
1 a .\: c h
f.'~
d :i. n
t ()
t
h
(~~
h
(-:~
x
1 a
t
c h ,
U~?'
(I .
The
s
f.~
t
E~
n
han c:
E~ M f.~
n
t
bit
:i. s
latched at the saMe tiMe
(by LCGAX) into Ut8.
At this tiMe
EN6
is fed
to the character
ROM
to provide the character
ROM
address selection for
its correspondinq character.
The attribute bits,
ENO-EN3,
output frOM
U29 are then sent to the 74LS163,
U210.
In this Mode,
with the count
enable inputs
P
and
T
qrounded,
it acts as a
latch with a synchronous
load and clear,
This
latch
provides the
additional character
tiMe
delay to COMpensate for the character
ROM
access
tiMe.
If
the
set
f.H)
h
":H·, C
f:~ I"H:-:n
t
bit
>
EN 4, :i.
~:;
I:)
f.~
t,
t
h
f.~
0 lJ
t
P
lJ
t,
U
1.
Bpi
n
~3,
wi
11 q
0
1 ()
was the
bit is
latched.
This
activates
the load
input of U210 causing the
attributes to be loaded on the next character clock (when the character
ROM
outputs are loaded into the shift reqister).
VIDEO (.:\ ITR IHUTES
The bli.nk dttribute output
(U210 pin 14)
is gated
with the blinkrate
~:~:i.qnal
{-'{'Of"'!
thf.~
I/O
~:~(~~cti()n,
which
altE~rnatf~~:;
hiqh and
low
to
pr'oduce
the active
low
NBLINK
signal.
When
active the
NBLINK
signal allows
() n :I. y
t
h
f..~
CUT'~; 0 l'
t
0
b
(~~
d i
~:)
p
".I.
I:)
y
f.~
d ,
b ]. a n k :i. n
~~
t
h
f.~
c: hal'
i:\
c:
t
f.~ l' .
In
t
h i
£)
way,
·tl·,(~~
1:11 :i.nl<:i.nq
char'i:\c:t~:-~(·,·::;
ar'f.!
i~l t(~rnat(:~ly
d:i.~:;plaYf.~d
and
bli!tnl(~?d.
Thf:~
inverse bit siMply selects the inverted dot
streaM
(ALPHA)
or cursor
~:;:i.qnal'::;,
.
Advertisement
