Eprom Programmers Handbook CSM

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INTRODUCTION TO EPROMSWhat i s a EPROM? How d o y o u p r o g r a m t h e m ? Why w o u l d y o u w a n t t o p r o g r a m an EPROM? Once i t i s p r o g r a m m e d w h a t d o y o u d o w i t h i t ? D u r i n g t h e c o u r s e o f t h i s m a n u a l we w i l l a n s w e r t h e s e and o t h e r q u e s t i o n s a b o u t EPROMs. O f a l l t h e v a r i o u s f a c e t s o f home c o m p u t i n g , EPROMs a r e o n e o f t h e l e a s t u n d e r s t o o d a n d t h e m o s t u s e f u l . V e r y l i t t l e i s known b y t h e a v e r a g e u s e r a b o u t EPROMs o r how t o u s e them. Many p e o p l e a r e a f r a i d o f o p e n i n g u p t h e i r c o m p u t e r s , d i s k d r i v e s and c a r t r i d g e s . They d o n ' t r e a l l y know w h a t t h e y a r e l o o k i n g a t , how t h e c h i p s w o r k o r w h a t t h e y d o . Y e t , when a u s e r b e g i n s t o u n d e r s t a n d t h e p o w e r and v e r s a t i l i t y o f EPROMs, o n e becomes h o o k e d . A type o f a d d i c t i o n soon t a k e s o v e r t h e u s e r ; before long y o u ' l l find y o u r s e l f w a n t i n g t o p u t a l l o f y o u r f a v o r i t e p r o g r a m s on EPROM. P r o g r a m s , o n c e p u t o n an EPROM, r e q u i r e v i r t u a l l y n o t i m e a t a l l t o l o a d . I m a g i n e t u r n i n g on y o u r c o m p u t e r and i n s t a n t l y h a v i n g y o u r f a v o r i t e word p r o c e s s o r , d a t a base, s p r e a d s h e e t o r u t i l i t y up and r u n n i n g . J u s t b y p l u g g i n g i n a c a r t r i d g e and t u r n i n g o n y o u r computer you can be r e a d y t o g e t t o work! No l o n g LOAD t i m e s , w h a t u s e d t o t a k e m i n u t e s t o l o a d may r e q u i r e o n l y a i t is f r a c t i o n o f a second f r o m a c a r t r i d g e . Not o n l y t h a t , p o s s i b l e t o p u t many d i f f e r e n t p r o g r a m s o n a s i n g l e c a r t r i d g e a n d p i c k y o u r f a v o r i t e f r o m a menu. L e t ' s t a k e a q u i c k l o o k a t some o f t h e d i f f e r e n t p o s s i b i l i t i e s t h a t t h e u s e o f EPROMs b r i n g t o mind: 1. P u t t i n g a s i n g l e p r o g r a m o n a c a r t r i d g e 2. P u t t i n g a number o f d i f f e r e n t p r o g r a m s o n a s i n g l e c a r t r i d g e w i t h a menu t h a t a l l o w s y o u t o s e l e c t t h e d e s i r e d one.

3. U s i n g BANK SWITCHED c a r t r i d g e s t h a t a l l o w y o u t o p u t 256K o f memory o n a s i n g l e b o a r d . T h i n k o f a l l t h e v a r i o u s p r o g r a m s t h a t y o u w i l l f i t i n 2 5 6 K ! ! You c a n a d d a menu t h a t a l l o w s y o u t o p i c k and c h o o s e p r o g r a m s a t w i l l .

4.

M o d i f y i n g t h e KERNAL o r BASIC R O M o f t h e c o m p u t e r s o t h a t y o u h a v e y o u r own t o t a l l y c u s t o m i z e d c o m p u t e r . I t i s p o s s i b l e t o change s c r e e n c o l o r s , t i t l e messages on power-up, default d e v i c e n u m b e r s and much m o r e .

5. M o d i f y t h e DOS ( D i s k O p e r a t i n g S y s t e m ) f o r a custom d i s k d r i v e . E x t r a t r a c k s and s e c t o r s , h i g h speed d a t a t r a n s f e r r o u t i nes. 6. Use t h e PROMENADE a s d e v i c e #16. T h i s a l l o w s y o u LOAD and S A V E f i l e s f r o m EPROMs, a s y o u w o u l d o n y o u r d i s k d r i v e . Imagine l o a d i n g y o u r f a v o r i t e p r o g r a m f r o m an EPROM. can be used i n o t h e r computers. PROMENADE may b e u s e d t o p r o g r a m a w i d e v a r i e t y o f E P R O M S . The

7. P r o g r a m EPROMs t h a t

EPROM HANDBOOK

INTRO TO EPROMs

PAGE 1

8. C r e a t e y o u r own, t o t a l l y new, o p e r a t i n g s y s t e m f o r t h e C-64 ( o r o t h e r c o m p u t e r ) and end up w i t h a s p e c i a l i z e d , dedicated computer. T h i s i s e x t r e m e l y u s e f u l i n s c i e n t i f i c a p p l i c a t i o n s , b u s i n e s s and i n d u s t r i a1 c o n t r o l a p p l i c a t i o n s .Now t h a t we h a v e l o o k e d a t some o f t h e a p p l i c a t i o n s l e t ' s e x a m i n e a f e w o f t h e f u n d a m e n t a l s o f EPROMs a n d E P R O M p r o g r a m m i n g . L e t ' s s t a r t o f f b y l o o k i n g a t w h a t an E P R O M i s and how i t w o r k s . an e l e c t r o n i c s t o r a g e An EPROM i s a t y p e o f memory c h i p , i .e., device, s i m i l i a r i n n a t u r e t o a disk. Data, programs o r o t h e r t y p e s o f i n f o r m a t i o n c a n b e p u t o n t o an E P R O M f o r l a t e r r e c a l l , j u s t as t h e same d a t a may b e s a v e d t o a d i s k a n d l a t e r r e c a l l e d . D a t a may b e e r a s e d f r o m an E P R O M a n d t h e E P R O M may be reprogrammed, s i m i l i a r t o e r a s i n g and c o p y i n g a d i s k . EPROMs a r e r e l a t e d t o o t h e r t y p e s o f memory c h i p s s u c h as ROMs 'Read o n l y ' means and PROMs. ROM s t a n d s f o r Read O n l y Memory. t h a t we c a n o n l y r e a d i n f o r m a t i o n f r o m t h i s memory c h i p , not w r i t e t o i t . T h a t i s , we c a n e x a m i n e and u s e t h e i n f o r m a t i o n c o n t a i n e d i n a ROM, b u t we c a n ' t c h a n g e i t . R O M c h i p s come p r e - p r o g r a m m e d d i r e c t l y f r o m t h e m a n u f a c t u r e r and c a n n o t b e c h a n g e d o r m o d i f i e d i n a n y way. Once a R O M i s programmed i t w i l l r e t a i n i t s d a t a i n d e f i n i t e l y , w i t h o u t r e q u i r i n g any power t o do s o . I n o t h e r w o r d s , we may t u r n t h e c o m p u t e r ' s p o w e r o f f and when i t i s t u r n e d back on t h e ROM w i l l h a v e r e t a i n e d a l l t h e d a t a . PROM s t a n d s f o r P r o g r a m m a b l e Read O n l y Memory. The word ' P r o g r a m m a b l e ' r e f e r s t o t h e f a c t t h a t t h e u s e r may p r o g r a m t h i s i s chip. T h i s programming i s a one-shot affair; once i t programmed t h e c o d e may n o t b e a l t e r e d o r e r a s e d . I n t h i s m a n n e r t h e P R O M i s v e r y c l o s e l y r e l a t e d t o t h e ROM. L i k e t h e R O M y t h e PROM does n o t r e q u i r e any power i n o r d e r t o r e t a i n i t s d a t a . N e x t we h a v e t h e EPROM, E r a s e a b l e P r o g r a m m a b l e Read O n l y Memory. The E P R O M may be programmed a n d e r a s e d t h o u s a n d s o f t i m e s . The E P R O M w i l l p e r f o r m i d e n t i c a l l y t o a R O M when i t i s i n s t a l l e d i n a c i r c u i t . As b e f o r e , t h e E P R O M d o e s n o t r e q u i r e a n y p o w e r i n o r d e r t o r e t a i n i t s d a t a . The m a j o r d i f f e r e n c e comes when i t i s t i m e t o change o r m o d i f y t h e d a t a c o n t a i n e d on t h e c h i p . W i t h a ROM o r a P R O M i t i s n o t p o s s i b l e t o r e p r o g r a m them, w h e r e a s an E P R O M may be e r a s e d and r e - p r o g r a m m e d . One c a n e a s i l y s e e t h a t i t i s v e r y a d v a n t a g e o u s t o h a v e a c h i p t h a t may be r e u s e d t i m e a n d t i m e again. C l o s e l y r e l a t e d t o ROM, PROM, and E P R O M i s t h e R A M c h i p . RAM, w h i c h i s Random A c c e s s Memory, means t h a t we c a n r e a d O R w r i t e t o any b y t e o n t h e c h i p a n y t i m e we w a n t . A n o t h e r d i f f e r e n c e b e t w e e n R A M and ROM i s t h a t t h e c o n t e n t s o f R A M d i s a p p e a r when t h e power i s r e m o v e d . ROMs, on t h e o t h e r hand, h o l d o n t o t h e i r d a t a w i t h o u t n e e d i n g any p o w e r . The o p e r a t i n g s y s t e m o f t h e C-64 i s s t o r e d i n a t y p e o f R O M s o i t i s i n s t a n t l y a v a i l a b l e when t h e m a c h i n e i s p o w e r e d u p . The t e r m R O M i s s o m e t i m e s u s e d l o o s e l y t o i n c l u d e PROMs and EPROMs t o o .

EPROM HANDBOOK

INTRO TO EPROMs

PAGE 2

Remember, t r u e ROMs h a v e t o h a v e t h e i r i n f o r m a t i o n p u t o n a t t h e f a c t o r y , s o t h e y a r e n ' t much u s e t o u s . Much m o r e u s e f u l i s a PROM - a P r o g r a m m a b l e ROM. ' P r o g r a m m a b l e ' means t h a t we c a n p u t w h a t e v e r i n f o r m a t i o n we d e s i r e o n t h e c h i p o u r s e l v e s , by 'programming' i t w i t h a s p e c i a l d e v i c e s u c h as t h e P R O M E N A D E ' p r o g r a m m e r ' . H o w e v e r , we c a n o n l y p r o g r a m a t r u e P R O M o n c e s i n c e t h e r e i s n o way t o e r a s e i t . T h i s b r i n g s u s t o EPROMs. An EPROM i s an E r a s a b l e PROM. N o t o n l y c a n we p r o g r a m t h e c h i p o u r s e l v e s , b u t we c a n a l s o e r a s e a n d r e p r o g r a m i t many t i m e s . Erasing the c h i p i s n o t t h e same a s w r i t i n g t o i t , f o r t w o r e a s o n s . First, t h e e n t i r e c h i p i s e r a s e d a t t h e same t i m e , w h e r e a s t h e c h i p i s w r i t t e n t o o n e b y t e a t a t i m e . Second, when an E P R O M i s e r a s e d , each b i t o f t h e e n t i r e c h i p i s f i l l e d w i t h 1 ' s . Writing t o ( p r o g r a m m i n g ) an E P R O M c a n o n l y c h a n g e a 1 b i t t o a 0 b i t . When an E P R O M i s programmed t h e o n l y b i t s t h a t g e t c h a n g e d a r e t h o s e EPROMs a r e e r a s e d t h a t c o n t a i n 0 ' s . The 1 b i t s a r e l e f t a s i s . u s i n g s p e c i a l u l t r a v i o l e t (UV) light. C o m p l e t e e r a s u r e o f an EPROM g e n e r a l l y t a k e s f r o m 5 t o 15 m i n u t e s . The E P R O M h a s a v e r y s p e c i a l r e l a t i v e c a l l e d t h e EEPROM. The EEPROM i s an E l e c t r i c a l l y E r a s e a b l e PROM. T h i s means t h e E E P R O M m