Low V O L T A G E S E N S O R - Tandy 1000 SL Technical Reference Manual

2 - 2 - 1 - 4 . Low v o l t a g e s e n s o r
-
LVS (U2-32)
The low v o l t a g e s e n s o r
( L V S )
i s equipped t o p r o t e c t t h e F D D from
erroneous o p e r a t i o n due t o t h e i n t e r n a l c i r c u i t c o n s t r u c t i o n of t h e F D D
d u r i n g u n s t a b l e s t a t e of t h e power v o l t a g e such a s a t power on o r o f f .
Two
s e n s o r s
o f
LVSO and
L V S l
a r e equipped i n t h e read w r i t e LSI, U2.
LVSO
monitors t h e
+5V
v o l t a g e s u p p l i e d t o t h e i n t e r n a l c i r c u i t of t h e
read w r i t e
L S I .
If
t h e v o l t a g e i s lower than
3 . 5 V
through
4 . 4 V ,
it
s u p p l i e s s i g n a l s t o i n h i b i t t h e o p e r a t i o n of t h e common d r i v e r , w r i t e
d r i v e r , e r a s e d r i v e r , and w r i t e c o n t r o l l o g i c i n t h e LSI, which p r o t e c t
t h e d i s k from t h e erroneous w r i t e o r erroneous e r a s e d u r i n g u n s t a b l e
s t a t e o f t h e power v o l t a g e .
/ \
i -
L V S l
i s equipped t o g e n e r a t e
s i g n a l t o be s u p p l i e d t o t h e c o n t r o l
c i r c u i t i n item
2 - 2 - 2 .
AS
w e l l a s LVSO, it i s
a c t i v a t e d i n t h e range
o f
3 . 5 V
through
4 . 4 V .
The monitored v o l t a g e by t h e
L V S l
i s o n l y
+5V
connected t o t h e
LVGG
t e r m i n a l ( p i n 3 7 ) of t h e r e a d w r i t e
L S I .
While
t h e
E
s i g n a l i s
LOW
l e v e l , a l l t h e c o n t r o l c i r c u i t s (mainly c o n t r o l
L S I ,
U1) a r e r e s e t .
(Fig.206)
Typical
waveform o f low v o l t a g e sensor
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