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8 - 1 3 1 .
T h e t r i g g e r l i g h t s u b ro u t i n e I S b y p a ssed w h e n e v e r t h e t i m e r i s ru n n i n g . W h e n t h e
t i m e r ru n s o u t , t h e f i ve q u a l i f i e rs i n states 1 0 1 t h rou g h 1 05 a re e xa m i n ed , b y p r i o r i ty , to u p d a te
t h e i n d i cato r l i g h t s . State 1 0 1 c h e c k s t h e s t a t u s of t h e Sta rt L i t e q u a l i f i e r. I f n e i t h e r c h a n n e l
sta rt l i g h t i s o n , t h e p r o g ra m sta rts t h e ti m e r state 1 35 , a n d p ro c ee d s to state 1 38 . States 1 38
th ro u g h 1 48 f o r m a b ra n c h t h a t e xa m i n e s t h e X - Y q u a l i f i e r a n d t h e s t o p a n d sta rt p r o b e s e l e c t
s w i t c h e s . T h e b ra n c h ro u t i n e t u r n s o n t h e s t o p a n d sta rt c h a n n e l s e l ected , a n d t u rn s o f f t h e
l i g h ts n o t s e l ected . W i t h t h e t i m e r r u n n i n g , s t a t e 1 48 j u m p s to state 1 36 w h e re the S t o p P u l s e
q u a l i f i e r i s c hec ked . If n o s t o p p u I s e h a s occ u r re d , s t a t e 1 37 j u m ps to s t a t e 1 20 wh i c h s t a r t s t h e
t i m e r a n d ret u r ns to t h e m a i n p rog ra m .
8 - 1 32 . States 1 03 t h r o u g h 1 08 a n d 1 3 1 th ro u g h 1 34 f o r m a n o t h e r b ra n c h , T h i s b ra n c h reacts to
a t ra n s i t i o n by a sta rt p u l s e state 1 03 o r a st o p p u l s e state 1 04 by t u r n i n g off the a p p r o p r i a t e
l i g h t . I f b o t h a sta rt a n d s t o p p u l se h a ve occ u r red , t h e F i rst q u a l i f i e r state 1 05 d e te rm i n e s
w h i c h wa s f i rst. Afte r t h e l i g h t i s t u r n e d o f f , t h e p ro g ra m j u m p s to state 1 20 w h i c h sta rts t h e
ti m e r a n d ret u r n s to t h e m a i n p r o g ra m . T h e m a i n p r o g ra m w i l l c o n t i n u o u s l y c yc l e th ro u g h t h e
i d l e l o o p u n t i l t h e t i m e r c i rc u i t t i m e s o u t , at w h i c h t i m e t h e t r i g g e r l i g h t s u b ro u t i n e c a n be
ree n t e red and t h e l i g h t s u pd a ted .
8 - 1 33.
T h e T i m e Z e ro s u b ro u t i n e c o n s i sts of states 247 th ro u g h 2 5 2 . T h i s c o m m a n d stri n g i s
e n t e red w h e n t h e f ro n t p a n e l T I M E Z E R O/ L EV E L s w i t c h i s r a i sed to T I M E Z E R O p o s i t i o n ,
C o m m a n d L ATCH 1 5 state 247 d ri ves o u t p u t 1 5 p i n 1 7 o f A 1 U 1 0 1 0 w , effe c t i ve l y ze ro i n g a l l
fo u r t h u m b w h ee l s w i t c h o u t p u t d a t a l i n e s t h ro u g h d i o d e s C R 9 t h ro u g h C R 1 2 . State 248 resets
the A2 DAC a sse m b l y to z e r o . States 249 t h ro u g h 252 now l o ad zeros in as ref e re n c e v o l t a g e
f o r S t a r t a n d S t o p c h a n n e l s . T h e D A C wi I I c o n t i n u e to be r e s e t a n d z e roed a s l o n g a s t h e T I M E
Z E R O s w i t c h i s ra i sed .
8 -1 34.
T R O U B L E S H O O T I N G
8 - 1 35 .
F o r t r o u b l e sh o o t i n g p u r p oses , the o p e ra t i o n o f t h e 536 3 8 m a y b e d i vi d ed i n to two
major f u n c t i o n a l a re a ; t h e R F sect i o n and t h e l o g i c c o n t ro l sec t i o n . T h e RF sec t i o n i n c l u d e s
t h e p ro b e s , c h a n n e l s w i t c h e s , c o m pa ra t o r s , o u t p u t d ri ve rs , a n d p o w e r s u p p l y . I t c o n ta i n s t h e
c o m p l e te s i g n a l p a t h f ro m p r o be t i p to o u t p u t 8 N C . T h e l og i c c o n t r o l sec t i o n i n c l u d e s t h e
state mac h i n e w i t h a ssoc i a ted c i rc u i t ry , ca l i b ra t i o n a n d refe re n c e D A C s , a n d S a m p l e a n d
H o l d Refe re n c e A m p l i f i e rs .
8-1 36 .
To l oca l i ze a p ro b l e m , f i rst d e te rm i n e w h i c h of t w o maj o r f u n c t i o n a l a reas i s a fa u l t .
T h e f u n c t i o n a l o p e ra t i o n o f t h e R F sec t i o n c a n b e ve ri f i e d b y S i m u l a t i n g a T i m e Z e r o
ca l i b rati o n , p a ra g ra p h 3 - 1 3 . T h i s proced u re i nj e c t s a st re a m of p u l s e s 6 Il S n e g a t i ve p u l se s at
20 kHz I n to b o t h p ro b e ti p s . T h ese p u l ses can be t ra c ed t h ro u g h the i n d i vi d ua l c h a n n e l stages
u s i n g a n osc i l l o s c o p e and sta n d a rd s i g n a l t rac i n g proced u re s .
8-1 37 .
Tro u b l e s h o o t i n g t h e l o g i c c o n t ro l se c t i o n req u i re s a t h o r o u g h k n o w l e d g e of b o t h t h e
h a rdwa re o p e rati o n a n d t h e state m ac h i n e p r o g ra m . R efe r to T h e o r y of O p e ra t i o n , pa rag ra p h
8 -5 7 , f o r a n ove ra l l i n st ru m e n t b l oc k d i ag ra m d i sc u s s i o n , a s we l l a s d e ta i l e d desc ri p t i o n s of
the state m a c h i n e a n d f l o wc h a rt o p e ra t i o n pa rag ra p h 8-95
8 - 1 38.
State Machine Tro u b le s h ooti n g Tec h n i q u e s
8-1 39 .
T h e f o l l o w i n g pa ra g ra p h s d e s c r i b e two s e p a rate m e t h o d s of t ro u b l e s h o ot i n g t h e
state mac h i n e . T h e f i rst m e t h od u s e s t h e 5 0 0 4 A S i g n a t u re A n a l yz e r . T h i S i n v o l ves a s i m pl e
ho o k u p p roced u re a n d a n o d e - b y- n o d e e xa m i n a t i o n , u s i n g t h e s i g n a t u re ta b l es p r o v i d e d . T h e
s e c o n d m e t h o d s u s e s t h e 1 60 0 A Log i c A n a l yz e r a n d req u i res a m o r e c o m p re h e n s i ve
u n d e rsta n d i n g of t h e f l o wc h a rt a n d state m a c h i n e t h e o r y .
M od e l 5363 8
S e r v i c e
8 - 3 1
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