Lever Lock Solenoid; Read/Write Head Positioner; Step And Direction; Stepper Motor Control - Tandy 6000 Service Manual

A lo w , a c tiv e s ig n a l is s u p p lie d to th e L S I c h ip ,
w h ic h s u p p lie s a n a c tiv e s ig n a l to th e m ic r o ­
pro ce ssor a n d e n a b le s th e in p u t a n d o u tp u t
s ig n a ls in t e r n a lly .

LEVER LOCK SOLENOID

W h e n th e le v e r lo c k s o le n o id o p tio n ju m p e rs
a re in s ta lle d a n d th e d r iv e is s e lected, th e re is
a h ig h o u tp u t o n P in 16 o f th e m ic ro p ro c e s s o r.
T h is s ig n a l is in v e r te d a n d e n e rg iz e s th e le v e r
lo c k so le n o id .
4.4 READ/WRITE HEAD
POSITIONER
T h e c o m p o n e n ts o f th e d r iv e r e q u ir e d to p o s i­
t io n th e r e a d /w r ite h eads a t th e d e s ire d tr a c k
a re :
1. S te p a n d D ir e c tio n C ir c u its
2. S te p p e r M o to r C o n tro l C ir c u its
3. S te p p e r M o to r
S tep O u t T o w a rd T ra c k 0
Pin
Num ber
0
P 7-1 0
P 7 -2 1
P 7 -3 0
P 7 -4 1
TABLE 4-1
STEPPER LOGIC TRUTH TABLE
Phase
1
3 2 0
1 1 0 0
1
0 0 1
0
0 1 1
0
1 0 1

STEP AND DIRECTION

T h e S te p a n d D ir e c tio n s ig n a ls a re d e riv e d
fr o m th e h o s t c o n tr o lle r v ia in te r fa c e co n n e c­
t o r P I , P in 36, a n d P I , P in 34, re s p e c tiv e ly .
T h e S te p a n d D ie c tio n s ig n a l is s u p p lie d to th e
L S I c h ip a n d
se le ct. I f th e d r iv e is n o t se lected, o r th e d r iv e
is t r y in g to w r it e
d is a b le d .
T h e S te p a n d D ir e c tio n s ig n a ls a re th e n s u p ­
p lie d to th e m ic ro p ro c e s s o r.

STEPPER MOTOR CONTROL

T h e m ic ro p ro c e s s o r g e n e ra te s th e fo u r phases
o f th e s te p sequence based on in fo r m a tio n
fr o m th e s te p a n d d ir e c tio n in p u ts . T hese fo u r
phases a re fe d to th e s te p p e r m o to r d riv e rs ,
w h ic h p ro d u c e
m o to r 's c o ils (F ig u re 4-7).

STEPPER MOTOR

T h e s te p p e r m o to r is a b ip o la r, fo u r-p h a s e
m o to r, w h ic h ro ta te s
p h a se (T a b le 4-1). T h e c a p s ta n a n d s p lit b a n d
tra n s la te s th is r o ta tio n to a one t r a c k lin e a r
m o v e m e n t o f th e h e a d c a rria g e a s s e m b ly .
S te p In T o w a rd T h e In n e r T ra c k s
Pin
Num ber
0
P 7 -1 0
P 7 -2 1
P 7 -3 0
P 7 -4 1
4-6
g a te d in t e r n a lly w i t h
d a ta , s te p p u ls e s
th e c u r r e n t th r o u g h
1.8 degrees f o r e ach
Phase
1 2
3
0
1 1
1 0 0
1
1 0
0 1
0
d r iv e
a re
th e
0
0
1
0
1