P i n
S i g n a l
Pin ,
S i g n a l
number
name
number
name
19
Signal Ground
I
20
I
INDEX PULSE
. I
I
S i g n a l G r o u n d
36
I
STEP
21
Signal Ground
22
DRIVE READY
23
24
25
Signal
Ground
26
DRIVE 0
37
Signal Ground
I
38
WRITE
DATA
S i g n a l G r o u n d
I
W R I T E
I
Signal Ground
I
42
I
I
45
Signal Ground
44
WRITE PROTECT
S i g n a l
G r o u n d
46
READ DATA
I
-
-
-
-
-
-
-
I
49
I
-
-
-
-
-
-
-
I
I
Centronics Standard Printer Interface
I n a s t a n d a r d s p e c i f i c a t i o n o f t h e F o r m u l a - l , P a r a l l e l I / O
P o r t c a n b e c o n n e c t e d w i t h t h e C e n t r o n i c s S t a n d a r d I n t e r f a c e
P r i n t e r d i r e c t l y .
A s p i n a s s i g n m e n t o f t h e P a r a l l e l I / O c o n n e c t o r h a s
n o
full
c o m p a t i b i l i t y t o
t h e
C e n t r o n i c s
P r i n t e r S p e c i f i c a t i o n ,
f o r d e t a i l s r e f e r t o T a b l e 4 Cable Connection for External
P r i n t e r
T h e l o g i c
o f
P a r a l l e l I / O P o r t s
a r e s h o w n
i n t h e f o l l o w i n g
p a g e < F i g . 4 L o g i c o f P a r a l l e l I / O P o r t s > .
B e s i d e s
t h e o t h e r
s i g n a l s , t h e P a r a l l e l I / O P o r t s p o s s e s s ,
t h e s i g n a l s
o f
T h e
e x p l a n a t i o n o f t h e s e s i g n a l s
a r e a s
f o l l o w s .
1 .
( D M A
Input
T h i s
s i g n a l i s a c t i v e ‘ L o w ’ ,
Parallel I/O
f o r
D M A t r a n s f e r .
and available when using
U s i n g t h i s s i g n a l , i t i s
necessary to set up the parameter in the DMA
c o n t r o l l e r .
This signal is connected
t o t h e ‘ R D Y ’
t e r m i n a l o f D M A
c o n t r o l l e r .
2 .
COUNT (DMA transfer
COUNT)
Output
T h i s
signal is
a c t i v e ‘ L o w ’
a n d p r o g r a m m a b l e , a n d w h e n
t h e n u m b e r
o f b y t e o f
D M A t r a n s f e r r e a c h e s a s e t v a l u e , a
p u l s e s i g n a l i s o u t p u t .
T h e r e a f t e r ,
d a t a t r a n s f e r o n e p u l s e b e i n g o u t p u t .
e v e r y 2 5 6 b y t e s
o f
3 .
C L
O C
K )
Input
T h i s s i g n a l
is
a c t i v e ‘ L o w ’ , a n d i t i s t h e i n p u t s i g n a l
o f t h e E x t e r n a l
C l o c k a t t h e t i m e
o f
t h e C h a n n e l
o n
‘ C o u n t e r
M o d e ’ o f
C T C .
See < Fig.
L o g i c
C o u n t e r
> .
T a b l e 2 C o n n e c t o r S i g n a l o f 8 ’
F l o p p y D i s k
D r i v e