T ABLE 3 - 1
D RIVE INTE R F A C E L I NE S A N D
P I N A S S I G N M E N T S
Ground
Pin
Signal
1
l 1
43
45
47
49
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
3
5
7
l A
'+8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
6
8
2
4
Write Current Switch
Motor On Control 1
Motor On Control 2
True Ready, (Motor On Control 3, Optional)
Two Sided (Strappable) (TM848-2E only)
Disk Change (Strappable)
Side Select (TM848-2E only)
In Use Indicator (Strappable)
Head Load Line/Motor Control
Index
Ready
Motor On Control 4
Drive Select 1 (Side Select Option, TM848-2E only)
Drive Select 2 (Side Select Option, TM848-2E only)
Drive Select 3 (Side Select Option, TM848-2E only)
Drive Select 4 (Side Select Option, TM848-2E only)
Direction Select (Side Select Option, TM848-2E only)
Step
Write Data
Write Gate
Track v
Write Protect
Read Data
Alternate I/O
Alternate I/O
44
46
48
50
DIRECTION SELECT AND STEP LINES
(TWO LINES)
When the dr ive is selected, a true (low) pul se
on the Step line, with a t i m e du r a t ion greater
than on e m i c r o second, i n i t i a t e s t h e a c c ess
motion. The direction of motion is determin ed
b y the logic state of th e D i r e ction Select li n e
w hen a s t e p p u l s e i s i s s ued. Th e m o t i o n i s
toward the center of
the disk if
the Direction
Select line is in the true (low) state. The direc-
t ion of m ot ion i s away f rom th e center of t h e
disk if th e D i r e ction Select line is in th e f al se
(high) state.
To ensure p r oper p o si t i oning, t h e D i r e c t i on
S elect line should be stable at l e ast 1 m i c r o -
second. prior
to the corresponding rising edge
of the step pulse, and remain stable 100 nano-
seconds after
it.
Write commands. When th e signal l ogic level
is false (high), the in put control l i nes and the
output status lines are disabled,
The Drive Select address is
determined by a
select shunt on the circuit board. Drive Select
lines 1 through 4 provide a means of daisy
chaining a maximum of four drives to a
con-
t roller. Only one can be t r u e ( l ow ) a t a t i m e .
An undefined operation mi gh t r esult i f t w o or
more drives are assigned the same address or
i f tw o o r m o r e D r i v e S elect l i n e s ar e i n t h e
t rue ( l o w ) s t a t e s i m u l t a n eously. A Dri v e
S elect l i n e m u s t r e m a i n s t a b l e i n t h e t r u e
(low) st at e u n t i l a n y o p e r a t io n i n p r o g r ess
(Step, Read/Write) is completed.
U sing S i d e S e l ect o p t i on s 1 8 t h r o u g h 4 8 ,
Drive Select li nes may be used as Side Select
lines for the TM848-2E (see Section 3.6).
3-3