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Mal con d
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t ion
~:;
( w h
(~n
cur'
~; 0
r
i
~:)
not active)
siMply causes the dot streaM to be turned on
during
scan
line :1.3.
This is accoMplished
by gating the UI...INE signal with ULTIME
and
u
s
:i. n q
't
h
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u
1
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n
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i
9
h ,
thE! {'
e
b y act
:i.
vat in
9
t
h
Eo?
dot streaM.
A
probleM exists,
however,
when we want to position the
c:
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r'
~:;
() '{'
i:\
t
a
c hal" act
(:!
l'
P
0 ~:;
i t
i ()
n w h
(~! 7'
c!
\J 1' 1
d c! r'
lin
(-:!
i
~:;
a
c:
t
i
v~!
.
W (-:! can
n
0
:I. ()
n
q
(~~ f'
,..,
f:!
7'
(: : ! ],
y
II
D
I~
II
i
n
t
IH~
C lH' S 0 f'
i
n tot h E-! dot
~:;
t r'
(~
i:\ M
b
(-:!
c a u
~:;
e
i
t
1
i
e
~:;
0
n
the saMe scan line
as
the underline and therefore would never
be seen.
What
is done
instead is that when both are active
(NCUR
is
low and
UlINE is high), neither the cursor nor underline appear on the display.
This essentially disables
the underline at the cursor position
on the
d
i
<:~
p
:I.
a
y
p (' ()
d
u
c
:i. n
<;)
a
b 1
ink in
q
h
0
1
(-:!
:i.
nth f:! un
d
(-:!
r' 1 in e .
The N
C U
I~
' : :)
i
q
n
a 1
:i.
s
~:~ (.:.!
n 'l
:i. n
t
0
U
~.
1. (} pin 3 w h
:i.
c h,
IrJ
h E-! n act i v e ,
p
f'
E-!
V
(~n
t
s
the u n d
(-:! i' "
lin e s i q n a 1
frOM
being gnted
into the
dot streaM.
At
the saMe tiMe
the ULINE
signal
is sent into U19 pin
1.3
disabling the
NCURSOR
siqnal
which
n () "
M
a
J.
".I.
Y
q
E-!
n
(~! T'
a
t
f..!
S
t
h
€-~
c:
U l' ~) () l' .
T h
lJ
~;,
b () t h
a
7' €-!
dis a b 1
f:~
d .
T h
(~~
:I.
i:,\ S
t
i:\
ttl'
:i.
but
E! )
hi:)
1
of
b r'
:i
<;)
h t ,
~:; (.:~
1.
E-.'
<:
t s w h :i c h ()
f
t h
(~
v i
cI
(~ 0
in put son
t
h
(~~
a n a
:I. ()
q
~) W f..! (.:~
p b () a
l'
d
w:i.
11
l "
(.:.! C €-~
:i.
v
(~
the d () tin
f ()
l " Mat
j,
0
n .
W hen
the
halfbriqht attribute is activated the dot inforMation is inhibited frOM
th(-? NFUI...I...BRT output
(whic:h
(Jiv€-~s
full
intf:~n~;ity
c:hal'ac:t~?r'~;»
LJ1tc? pin
b,
by pulling Ut12 pin 4 low,
and is enabled through U110 pin 8 which
~:)(::!I'\
d
~:)
tI'\(~!
act:i.
V
E!
' . I. ()
W
d () tin
f () {'
Ma t
:i. ()
n () n
NI-IAl..FHI~
T t () t h
e-~
SWE~f:~p.
ENO"'ClF .... l.. I NE
Th(-:~
reMi:lininq
(~~nhanCE~Mf:~nt
bit, E.NS,
pel"fOrMS the
f.·~nd"-of'-line
function.
When
set,
this bit causes
the display to be blanked frOM the current
character position to the end of the row.
This eliMinates the need to
clear
both
character
and
enhanceMent data
in
order to
c:lear
the
display.
After being latched :in U29
the end-of'-line signal
is gated
tl'H' () ll<;)
h
LH
9
and
U? "l
1: ()
:I.
0
W EH' t h
(-:!
c: 1
e-~
a l' in put () f
lJ
21 ()
( pin 1).
T his
causes the enhanceMents to be cleared at the next character c:lock (when
(::hi:\l'ac:tEH'
ROM
output~:;
ar'e loadE!d into the shift
r'egi~;ter'..:;).
At
the
saMe tiMe
that U210 is cleared,
the endof'-line Signal is latched into
U17.
The Q'
output
(U17 pin B)
is sent back to the preset input to
hold the flip-flop in the cleared
state for the rest of the scan line.
At the end of the scan line the NLRCX (inverted line rate clock) clears
the
flip-flop
(clear
overrides preset).
At
the
saMe tiMe the
Q'
output,
NEOlDEL,
is qated
through U1i1 to ac:tivate the BLANK signal.
This signal
blanks the
display by
deselecting the alpha input,
only
allowing the cursor siqnal to be gated to the sweep.
The cursor signal
is allowed since it is necessary to be able to position the cursor even
in
a blanked field.
The
Q
output,
U17 pin 9,
is gated to the clear
input of
U21(} in
order to hold
the enhanceMent latch
in the cleared
~:;tate.
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