Text Tell PXP40, PX-1000 Service manual

TEXT TELL

TECHNICAL MANUAL

PX-1000 PXP40

IB!K|

-1-

SECTION A: PX1000

C O N T E N T S P a g e

1. GENERAL INFORMATION 2

1.1 Product Description 2 1 . 2 S p e c i ﬁ c a t i o n s 3

2. THEORY OF OPERATION 5

3 . S E R V I C E 1 6

3 . 1 D i s a s s e m b 1 y / A s s e m b 1 y 1 6

3.2Calibration 17

3.3 Test Procedure 18

4. REPAIR 22

4.1 Int roduct ion 22 4 . 2 M o d u l a r 2 2 4 . 3 L o g i c B o a r d 2 4

5 . A P P L I C A T I O N S 3 5

5.1 C-M\IL 35 5 . 2 C o m p a n y M e s s a g e C e n t e r 3 5 5 . 3 C o n n e c t i o n t o M o v i n g M e s s a g e D i s p l a y s 3 6

6 . A C C E S S O R I E S 3 7

6.1 Standard 37

6.2 Optional 37

7 . A P P E N D I C E S 3 8

pif.

7.1 Module Replacement List 38 7 . 2 C o m p o n e n t L a y o u t D i a g r a m s 3 9

7.3 Component Listing 42

■ * 7 . 4 S c h e m a t i c s 4 7

- S E C T I O N B : P X P 4 0

1. GENERAL 50

^ 2 . T H E O R Y O F O P E R A T I O N 5 2

3 . S E R V I C E 5 6

ist

4 . A P P E N D I C E S 6 0

l^t

-2-

CHAPTER 1

GENERAL INFORVIATION

1.1 PX1000 PRODUCT DESCRIPTION

T E X T T E L L ' s PX1000, t h e Pocket Te l e x is a pocketable d a t a

c o m m u n i c a t i o n s u n i t , f o r c r e a t i n g a n d s e n d i n g / r e c e i v i n g t e x t .

Text can be creat e d u s ing the stan d a rd QWERT Y k eyboa r d, a nd s tored

i n t h e u n i t ' s m e m o r y . T h e m e m o r y w i l l h o l d u p t o 7 , 4 0 0 c h a r a c t e r s , o r 4 t o 5 p a g e s o f s t a n d a rd A 4 . T h e t e xt i s v i e w e d o n a s i n g l e l i n e o f 4 0 c h a r a c t e r s L i q u i d C r y s t a l D i s p l a y . I n b u i l t i n t h e u n i t i s a n

e a s y t o u s e , y e t s o h i s ti c a te d w o r d p r oc ce s s or . Te x t c a n b e s e n t a n d r e c e i v e d b y t e l e p h o n e u s i n g t h e u n i t s o n

bo a r d si m p l e x a c o u st i c m ode m .

A l s o , t e x t c a n b e t r a n s f e r r e d t o a p r i n t e r o r c o m p u t e r , v i a a n

R S 2 3 2 C c o m p a t i bl e s e r i a l p o r t . V i a t h i s p o r t a l s o , t e x t c a n b e

r e c e i v e d f r o m a c o m p u t e r , o r o t h e r d a t a c o m m u n i c a t i o n s d e v i c e . T h e u n i t i s p o w e r ed f ro m a n i n t e r n al r ec h a rg e a bl e b a t t e r y p ac k , w h i c h

i s c ha rg ed f r o m a n e xt er na l a d a pt or . T h e u n i t w i l l o p e r at e f o r m or e t h a n ﬁ ve h ou rs a ft er a f u l l r ec ha r g e. T h e m e m o r y c on te n t s a r e k e p t a s l o n g a s t h e b a t t e r y p a c k i s c h a r g e d .

T h er e a re v i su a l i n d i c a t i o ns o n t h e L C D o f t h e q u a l i t y o f t e l ep h o n e

r e c e p t i o n , t h e a m o u n t o f m e m o r y u s e d , w h e n t h e b a t t e r y p a c k i s l o w , a s w e l l a s o t h e r t e x t i n f o r m a t i o n .

T h e r e i s a l s o a n a u d i o i n p u t / o u t p u t a u d i o s o c k e t w h i c h c a n b e u s e d

f o r s t o r a g e a n d r e t ri e v a l o f d a t a f r o m a s t a n d a rd t a p e r e c o r d e r .

R§

T h e r e a r e d i ff er e n t v er s i o n s o f t h e P X 1 0 0 0 a v a i l a b l e . T h e b as i c

u n i t i s t h e E n c r y p t v e r s i o n w h i c h c o n t a i n s t h e e x t r a f u n c t i o n e n a b l i n g t e x t t o b e e n cr y p t ed a c co r d i n g t o a k e y, w hi c h i s s e l e c t e d

b y t h e u s e r. T h e o r i g i n a l t e x t , o n c e e n c r y p t e d , i s p r a c t i c a l l y

impossible to retrieve without knowledge of the exact key.

T h e C al c v e r s i o n h a s , i n s t e a d o f t h e e n c r y p t f u n c t i o n , t h e

p o s s i b i l i t y t o d o b a s i c a r i t h m e t i c c a l c u l a t i o n s .

Pi5

1.2 SPECIFICATIONS

Genera 1

D i m e n s i o n s L e n g h t

Height

Width

Weight

Operating Temperature Range

Humidi ty Range

Storage Temperature Range

B^l

225 mm

85 mm 29 mm

450 g

-10 C to +40 C

0-95% Rh

-25 deg. C to 55 deg. C

Te c h n i c a 1

Power Supply

internal rechargeable 6V battery

rechargeable from external 12V DC

Power Consumption

adaptor. < 150 uA unit off

< 30 mA norma 1 use <" 50 mA transmit/receive mode

Battery Charge Current

Ulfﬂ^

Bat tery Li fe

50 mA h igh charge

<2 mA trickle charge

>5 hrs. (normal us e) after fu ll

recharge

fﬂm)

Memory capacity

ffﬁwj

8k (7.4k available to user)

Modem

i*a

Modulation Standard

Frequencies Baud Rates

Data Format

Par i ty

Header

S p e a k e r O u t p u t l e v e l

R e c e i v e r S e n s i t i v i t y

Serial Port

Vo1tage Levels

Baud Rate

Data Format

Par i ty

Input

Output

FSK CCITT V.23 mode 1, 600 Bd.

MARK 1300 Hz, SPACE 1700 Hz

300, 600 and 1200 selectable from keyboard

1 s t a r t - b i t , 7 d a t a - b i t s , L S B ﬁrst, 1 parity-bit, 2 stop-bits

Even

T r a n s m i s s i o n s t a r t s w i t h 0 . 5 s e c .

M A R K , f o l l o w e d b y 1 6 N u l l - B y t e s ,

( A S C I I 0 0 ) a t t h e s e l e c t e d b a u d ra t e , 0. 8 s e c M A R K , a n d 4 Nu l l

bytes S e t a t f a c t o r y t o m a x i m u m l e v e l

a l l o wa bl e b y Te le ph on e A u t ho ri ty

i n c o u n t r y o f s a l e .

<-30dBm.

MARK -3 to -15V, SPACE 3 to 15V MARK - 5V (+- 20%),SPACE 5V (+ -20%)

1200 Bd 1 s t a r t - b i t , 7 d a t a - b i t s , L S B

ﬁrst, 1 parity-bit, 2 stop-bits.

Even

f^s

Audio Socket

Vo1tage Leve1s

Input impedance

Signal Format

Input

Output

5 . 0 V p - p m a x .

1 . 6 V p - p i n 1 2 0 o h m 120 ohm.

FS K C CI TT V.23 6 00 Bd . S ta nd ar d

f™i

ffS

f™5

f™J

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CHAPTER 2

PX1000 THEORY OF OPERATION

T h e f o l l o w i n g i s a d e t a i l e d t e c h n i c a l d e s c r i p t i o n o f t h e t h e o r y o f

Jpl

operation of the PX1000, Version H.

PCWER SUPPLY

T h e P X 1 0 0 0 d e r i v e s i t s p o we r f r o m a b a tt e r y p a c k c o n t a i ni n g ﬁ ve

rechargeable, Ni-Cd cells, connected in series, each with a nominal

v o l t a g e o f 1 . 2 V. T h i s g e n e r a t e s a n o m i n a l v o l t a g e o f 6 V D C a t t h e b a t t er y i n p u t s , p i n s 1 a n d 2 , o n c o nn e c t or J 5 .

T h i s v o l t a g e i s a p p l i e d d i r e c t l y t o I C 7 , w h i c h i s a Q U A D - N A N D ,

JP!

7 4 H C 0 0 . T h i s I C c o nt r o l s t he p ow e r o n / o f f t o t h e r e m a i n de r o f t h e ci rcui t.

W h e n t h e u n i t i s o f f , p o w e r i s t u r n e d o n b y p r e s s i n g t h e k e y O N / S T O P.

T h i s k e y i s c o n n e c t e d t o t h e R E S E T i n p u t o f a b i - s t a b l e m a d e u p o f

t w o N A N D g a t e s o f I C 7 . I n t h e o f f s t a t e , t h e o u t p u t o n p i n 3 , I C 7 i s

l o w. W h e n O N / S T O P i s p r e s s e d , t h i s o u t p u t g o e s h i g h , t u r n i n g o n b o t h

t r a n s i s t o r s , T l a n d T 2 , v i a c u r r e n t - 1 i m i t i n g r e s i s t o r s R 8 a n d R 1 8 .

B e c a u s e o f z e ne r d i o d e , Z l , w h i ch i s 5 V7 , t h e v ol ta g e o n t he e mi tt er

o f T l , i s n o w 5 V. T h i s i s V C C . P u l l - u p r e s i s t o r , R 7 , h o l d s t h e

b i - s t a b l e i n s e t s t a t e . T h e b i - s t a b l e i s r e s e t b y a l o w p u l s e f r o m M P U p o r t P 2 2 , w h i c h t u r n s o f f T l a n d T 2 . A v o l t a g e c o n v e r t o r , I C 6 ( 7 6 6 0 ) , i s n o w p o w e r e d u p , a n d g e n e r a t e s a

v o l t a g e o f a p p r o x i m a t e l y - 5 V a t i t s o u t p u t , p i n 5 , u s i n g r e s e r v o i r a n d

pump capacitors, C6 and C7.

T h e m a i n R A M , I C 4 ( 6 2 6 4 ) , i s p o w e r e d d i r e c t l y f r o m t h e b a t t e r y p a c k ,

v i a d i o de s D 3 a n d D 4 , w h i c h e n s u r e t h e c o r r e ct s u p p l y v o l t a ge f o r

t h i s I C .

-6-

BATTERY CHARGE CCT.

T h e b a t t e r y c h a r g e c i r c u i t c o n s i s t s o f a d u a l v o l t a g e s e n s o r I C , a

7 6 6 5 , ( I C 8 ) , a n d a c u r r e n t d r i v e c i r c u i t c o n s i s t i n g o f t r a n s i s t o r s m

T 3 , T i l a n d T 1 2 , a nd r e s i st o r s R 37 , a n d R 4 2 . T h e o p e r a t i o n o f t h e

c i r c u i t i s s u c h t h a t d i s c h a r g e d b a t t e r i e s a r e i n i t i a l l y c h a r g e d a t a h i g h r a t e o f 0 . 3 C , w h e r e C i s t h e b a t t e r y c a p a c i t y , w h i c h i s 1 7 0 m A h , m

u n t i l t h e y r e a c h a s p e c i ﬁ c v o l t a g e , o f 7 . 5 V, a t w h i c h p o i n t t h e r a t e

i s r e d u c e d , t o a t r i c k l e r a t e , o f l e s s t h a n 0 . 0 1 C .

W h e n t h e c h a r g e r i s i n s e r t e d , 1 2 V D C a p p e a r s a t p i n 3 8 o f t h e h y b r i d .

T h e l o w l e v e l o f t h e b a t t e r y v o l t a g e i s d e t e c t e d a t S I o f I C 8 , w h i c h ;

t u r ns o n T 3 , v i a o u t p u t O U T 1 ( T 3 i s a ct u a l l y t u r n e d o n b y p ul l - u p

R 4 3 , a s O U T 1 i s n o w h i g h - i m p e d a n c e ) . T h i s , i n t u r n , t u r n s o n

t r a n s i s t o r s T i l a n d T 1 2 , v i a c u r r e n t - 1 i m i t i n g r e s i s t o r , R 4 1 . T i l « *

s h o r t s o u t r e s i s t o r R 4 2 , s o t h e c u r r e n t ﬂ o w i n g i n t o t h e b a t t e r i e s

i s e q u a l t o 0 . 7 V d i v i d e d b y t h e v a l u e o f R 3 7 , w h i c h i s 1 3 o h m s ,

g i v i n g a c h a r g e c u r r e n t o f a p p r o x i m a t e l y 5 0 m A . D i o d e D 8 p r e v e n t s m

r e v e r s e c u r r e n t t h r o u g h t h i s c i c r u i t f r o m t h e b a t t e r i e s . C a p a c i t o r

C 5 p r o v i d e s p o w e r s u p p l y d e c o u p l i n g . A f t e r a s h o r t w h i l e , t h e b a t t e r y v o l t a g e w i l l r i s e t o 7 . 5 V , w h i c h , w h e n d e t e c t e d b y S 2 o f I C 8 , w i l l c a u s e T 3 t o t u r n o f f ( b y s h o r t i n g m

i t s b a s e t o g r o u n d ) , a n d a l s o T i l a n d T 1 2 . N o w t h e c h a r g e c u r r e n t i s d e t e r m i n e d b y t h e v o l t a g e a c c r o s s R 3 7 a n d R 4 2 i n s e r i e s , g i v i n g a c u r r e n t o f a p p r o x i m a t e l y 1 m A . m

T h e a c t u a l l ev e l a t w h i ch t h e h i g h r a t e o f c h a r ge s w it c h e s o u t i s

d e t e r m i n e d b y p o t en ti o m e te r, P I .

I C 8 a l s o h a s a n o u t p u t p i n , O U T 2 w h i c h g i v e s a n i n d i c a t i o n t o t h e «

M P U w h e n t h e b a t t e r i e s a r e l o w, a n d n e e d r e c h a r g i n g . T h e l e v e l , a t

w h i c h t h i s o u t p u t s w i t c h e s , i s s e t b y t h e r e s i s t o r n e t w o r k R 1 2 , R 1 3 J

a n d R 1 4 ; a l o w o u t p u t i n d i ca t i n g l o w b a t te r i e s. R e s i s to r R 5 p u l l s t h e o u t p u t h i g h , w h e n t h e i n t e r n a l s w i t c h i s o f f . H

I n b u i l t h y s t e r i s i s i n I C 8 p r e v e n t s o u t p u t o s c i l l a t i o n . T h i s i n v o l v e s J o u t p u t s H I a n d H 2 , w h i c h c h a n g e s t a t e w h e n t h e t r i p p o i n t i s r e a c h e d ,

t h u s , v i a R I O a n d R l 1 , e f f e c t i v e l y c h a n g i n g t h e d e t e c t i o n l e v e l s . T h e

voltage must reach the new level, before the output will switch again.

f9i

(BSS

MPU CLOCK CIRCUIT

T h e h e a rt o f t he s y s t e m i s t h e m i c r o p r o cc e s s o r , w hi ch , l i k e e ve r y

o t h e r M P U , m u s t h a v e a c l o c k s o u r c e f r o m w h i c h t o o p e r a t e . ^ j

T h e c l o c k c i r c u i t f o r t h e m i c r o i s m a d e u p f r o m a 4 . 0 I v H z p a r a l l e l J

r e s o n a n t f u n d a m e n t a l c r y s t a l , AT c u t . T h i s , t o g e t h e r w i t h t w o

c a p a c i t o r s , C I a n d C 2 , p r o v i d e s a s i n e w a v e s i g n a l a t t h e M P U p i n s m

X TA L a n d E X TA L , o f 4 M H z i n f r e q u e n c y. T h i s i s d i v i d e d d o w n i n t e r n a l l y

i n th e M P U , s o t h a t t h e sy s t e m c l o c k i s 1 M H z .

p™j

. %f&\

-7-

MPU

Wh e n VC C is a pp l i ed t o t h e MP U , by p re s si n g ON / ST OP a s d e s cr i be d

a b o v e , t h e M P U c o m e s o u t o f r e s e t , a f t e r a d e l a y o f 2 0 m S , c a u s e d by th e R C n et wo rk , R 3 and C4 .

T h e s t a t e s o f p o r t s P 2 0 , P 2 1 , a n d P 2 2 i m m e d i a t e l y a f t e r c o m i n g

o u t o f r e s e t d e c i d e i n w h i c h m od e t h e M P U w i ll o p e r a t e . P 2 1 i s t ie d t o g r o un d , P 2 0 i s l o w b e c a u s e i t i s c o n n e ct e d t o t h e p o r t o f a n I C w h i c h

i s p o w e r e d d o w n , a n d P 2 2 i s p u l l e d h i g h , v i a R 7 . C o n s e q u e n t l y, t h e M P U

o p e r a t e s i n t h e M u l t i p l e x e d M o d e . T h i s m e a n s t h a t t h e D AT A b u s i s

m u l t i p l e x e d w i t h t h e l o w e r 8 l i n e s o f t h e A D D R E S S b u s .

Th e MP U in p ut s NM I an d ST B ar e ti e d to V CC , an d so , ar e al w ay s

inact ive.

T h e O N / S T O P k e y i s a l s o c o nn e c t e d t o t h e e x t e r n a l i n t e r r u p t i / p , I R Q .

T h i s i n pu t i s p u l l e d h i g h b y r e si s t o r R 6 , w h e n t h e O N / S T O P s w i t c h i s o p e n . D i o de D 5 p re ve nt s b a t te ry v o l t ag e a p p ea ri ng o n t hi s i n p ut .

D i o d e D 2 p r o v i d e s i m m e d i a t e r e s e t o f t h e M P U , o n p o w e r d o w n , b y r a p i d

discharge of C4. Swi t c h S I , be t w e e n MP U R S T an d G N D , is i n c l u d e d t o p r o v i de t h e

f a c i l i t y t o c o m p l e t e l y r e s e t t h e s y s t e m .

ADDRESS AND DATA BUSSES

*■ multiplexed. So, to be able to separate the different signals, there

* " T h e o u p u t s o f t h i s l a t c h a r e a l w a y s e n a b l e d , v i a p i n 1 , w h i c h i s

/Wl

A s m e n t i o n e d a b o v e , t h e d a t a b u s , a n d l o w e r a d d r e s s b u s a r e

i s a l at c h , I C 2 ( 7 4 HC 3 7 3) , u s ed f o r t h e a d d r e s s o ut pu t s .

t i e d t o g ro u n d . T h e s e o u t pu t s a r e c o n tr ol le d b y t h e a d d r e s s s t r o b e

s i g n a l , A S , w h i c h i s o u t p u t f r o m p i n 3 9 , o f t h e M P U . W h e n t h i s s i g n a l i s h i g h , t h e o u t p u t s w i l l f o l l o w t h e i n p u t s . W h e n t h e s i g n a l g o e s l o w , t h e o u t p u t s w i l l r e m a i n u n t i l t h e s i g n a l g o e s h i g h a g a i n .

T h e 8 - b i t d a t a b u s i s c o n n e c t e d t o R A M , ( I C 4 ) , R O M , ( I C 3 ) , a n d t h e K e y b o a r d . T h e u p p e r f o u r d a t a b i t s a r e c o n n e c t e d t o t h e L C D m o d u l e .

Th e ad d re s s b u s is c on n ec ted t o R A M, R OM a nd t o th e Ke y bo a rd . T h e u p p e r t w o a d d r e s s l i n e s , A 1 4 a n d A 1 5 , a r e c o n n e c t e d t o t h e

decoder, IC5.

T h e system i s a n 8 - b i t d a t a , 6 4 K m e m o r y s y s t e m .

#^)

-8-

DECODER

A d e c o d e r c h i p , I C 5 ( 7 4 H C 1 3 8 ) , i s u s e d t o d e t e r m i n e w h i c h p a r t

o f t h e c i r c u i t t h e M P U w i s h e s t o a d d r e s s a t a n y o n e t i m e . T h e

m e m o r y i s d i v i d e d i n t o f o u r e q u a l p a r t s , o f w h i c h t h e f o l l o w i n g

l o c a t i o n s a r e u s e d b y t h e p r o g r a m :

$ 0 0 0 0 - $ 0 0 1 F I n t e r n a l R e g i s t e r s $ 0 0 2 0 - $ 0 0 7 F E x t e r n a l M e m o r y s p a c e

$ 0 0 8 0 - $ 0 0 F F I n t e r n a l R A M

$ 0 10 0 - $ 1 F F F M a i n Ex t e r n a l R A M

$ 2 0 0 0 - $ 3 F F F n o t u s e d

$4000 - $4 001 KEYBOAR D $ 4 0 0 2 - $ 7 F F F n o t u s e d

$8 0 0 0 - $ 8 0 01 L Q vl $ 8 0 0 2 - $ D F F F n o t us e d $E000 - $FFFF EPROM

T h e i n p u t s t o t h e d e c o d e r a r e A 1 5 , A 1 4 a n d t h e E s i g n a l ( s y s t e m c l o c k )

from the MP U.

Any t i m e the M P U a d dr e s s e s a v a l i d p a rt o f t h e me m o r y m ap , t h e

r e l e v a n t o u t p u t w i l l g o l o w . O t h e r w i s e , a l l t h e o u t p u t s a r e h i g h .

EPROM

Th e pr og r am mem or y is c on ta i ne d in 8K E PR O M, IC 3 27 6 4, a nd is

l o c a t e d a t a d d r e s s $ C 0 0 0 i n t h e s y s t e m m e m o r y. I t i s e n a b l e d w h e n

t h e i /p ' s G l , C a n d B , t o t h e d e c o d e r , a r e a s f o l l o w s :

Gl C

1 1BX

T h is c o m b i n a t io n w il l b ri n g o u t p u t Y 6 l o w, w h i ch i s c o nn e c t ed t o t h e

chip enable i/p, CE, of the EPROM.

Th i s oc c ur s w he n a ny w he r e in m e mo r y ab o ve $ C 00 0 is a d dr e s se d . Be c au s e o n ly 8 k Ep rom i s u s ed , $C 0 00 t o $D FF F is r e du n da n t. W he n an y

o the r p l a c e i n mem o r y i s a d d r e ss e d , t h e E P R O M i s d i s a b l e d , bec a u s e C E

i / p i s h i g h , a n d s o , i t s d a t a o / p ' s a r e h i g h - i m p e d a n c e .

18?.

Y^sr

-9-

RAM

R A M is l o c a t e d a t a d d r e s s $ 0 0 0 0 i n me m o r y, a n d t a k e s u p 8 K . T h i s

i n c lu d e s t h e R A M i n t e r na l t o t h e m i c r o p r o c c es s o r w h i c h i s 1 2 8 B y t e s ,

a s w e l l a s t h e e x t e r n a l R A M , w h i c h i s a n 8 K H N 6 2 6 4 , I C 4 . T h e e x t e r n a l R A M i s u s e d m a i n l y f o r t e x t s t o r a g e , b u t a l s o i s u s e d b y t h e p r o g r a m . T h e p r og ra m u s e s u p t o 6 00 b yt es , l e a v i ng 7 .4 K a v a i l ab le f or t e x t

storage.

T h e r e a r e t w o c h i p s e l e c t i / p ' s t o t h e R A M I C , C S 1 a n d C S 2 . C S 1 , w h i c h

i s a c t i v e l o w , i s u s e d b y t h e d e c o d e r t o a c c e s s R A M d u r i n g n o r m a l r u n n i n g . I n t h i s s i t u a t i o n , C S 2 , w h i c h i s a c t i v e h i g h , m u s t b e h i g h .

In p o w e r d o w n m od e , t he c o n t ent s o f th e R A M IC m u s t b e p r o te c t e d f r o m c o r r u p t i o n , w h i c h c o u l d o c c u r w h i l e t h e p o w e r t o t h e M P U i s

d e c a y i n g , a n d i t s o u t p u t s a r e u n p r e d i c t a b l e . P o w e r o ff i s c o n t r o l l e d

b y t h e M P U . B e f o r e c ut t i n g p o w e r, t he M P U ﬁ r s t b r i n g s o / p P 1 3 l o w, w h i c h i s c o nn ec te d t o C S 2 . A l so c on ne ct ed t o t h i s p i n i s a p u l l- do wn

r e si s t o r , R l , w hi c h e n su r e s t h at t h e R A M r e ma i n s d i sa b l e d u n t i l

power-up again. D u r i n g r u n n i n g m o d e , R A M i s e n a b l e d w h e n t h e i n p u t s t o t h e d e c o d e r a r e

IP!

as f ol l ow s :

Gl C B

1 0 0

T h i s s i t u a t i o n o c c u r s w h e n t h e M P U a d d r e s s e s a n y l o a c t i o n i n m e m o r y,

b e t w e e n t h e l o c a t i o n s $ 0 0 0 0 t o $ 3 F F F. P o w e r t o t h e R A M I C i s f e d d i r e c t ly f r o m t h e b a t t e r y v o l t a g e , t o

V D D , p i n 28 , v i a d i o d e s D 3 a n d D 4 . T h i s e n s u r e s t h a t R A M c o t e n t s a r e

s a v e d , f o r a s l o ng a s t h e b a tt e r y v o lt a g e r e ma i n s a b ov e 5 . 9 V,

t h e o r e t i c a l l y. I n a c t u a l p r a c t i c e , t h e c o n t e n t s r e m a i n v a l i d f o r m u c h l o w e r v o l t a g e l e v e l s . B e c a u s e o f t h e l o w c u rr en t c o ns um pt io n o f t h e I C

i n s t a n d b y, r e s i s t o r R 1 7 e n s u r e s t h a t d i o d e s D 3 a n d D 4 a r e t u r n e d o n

f u l l y t o p r o v i d e t h e r e q u i r e d v o l t a g e d r o p f r o m t h e b a t t e r y v o l t a g e .

C a p a c i t o r C 2 4 p r o v i d e s p o w e r s u p p l y d e c o u p l i n g .

Sfﬂ

BSl

JP>

KEYBOARD

f™i

-10-

Pij

Th e k ey b oa r d is i n cl u d ed o n th e me m o ry m a p,

b u t i s e n a b le d s e p e ra t e l y

b y t h e M P U , via o u t p u t P1 6 .

T h e k e yb oa rd i s r ea d i n t h e f o l l o wi ng m a n n er . F i r st a q u i c k s c a n i s m a d e t o d e t e r m i n e w h e t h e r a k e y h a s b e e n p r e s s e d . T h i s i n v o l v e s

e n a b li n g t h e k e y b o ar d b y b r i n gi ng P 1 6 l o w . I f n o k e y i s p r e s se d, a ll

d a t a l i ne s w i l l b e h i g h. A p re ss e d k e y w i l l c a u se o n e d a t a l i n e t o g o

low, via a combination of two of resistors, Rl to R16. To identify

e x a c t l y w h i c h k e y h a s b e e n p r e s s e d , e a c h a d d r e s s l i n e , A 0 t o A 8 ,

i s b r o u g h t l o w i n d i v i du a l l y , a n d t h e d a t a b u s r e ad a s a b o v e .

LCM

The Liqu PX1000.

contai ne

mi ni atur

certain The LCM HD44780

characte g i v e s t h

The cont

The MPU

T h i s c o n

we 11 as

i d C r y s t a l D i s p l a y M o d u l e , t h e L C M , i s c u s t o m d e s i g n e d f o r t h e

I t i s a o n e l i ne X 4 0 c h a r a c t e r d i s p l a y, e a c h c ha r a c t e r

d i n a 5 x 7 d o t f o n t . A l s o o n t h e d i s p l a y a r e u p t o s e v e n

e ﬁ x e d m e s s a g e s , w h i c h a r e u s e d t o i n di c a t e t he s ta t u s o f f u n c t i o n s t o t h e u s e r .

is d r i v en b y f o ur H D 4 4 10 0 L C D se g m e n t/ c o l u mn d r i ver s a n d a

d o t m a t r i x c o n t r o l l e r . T h e c o n t r o l l e r I C a l s o c o n t a i n s

r gen e r a t o r R O M , a s w e l l a s c h arac t e r g e n e r a t o r R A M , w h i c h e u s e r a b i l i t y t o d e ﬁ n e u p t o 1 4 e x t r a c h a r a c t e r s . r a s t o f t h e L C D i s ﬁ x e d . c o m m u n i c a t e s w i t h t h e L C M v i a a t e n s i g n a l c o n n e c t i o n , J 2 . n e c t i o n c o n t a i ns t h e f o u r u p p er d a t a l i n e s D 5 t o D 7 , a s

the following :

+Vcc

p o w e r s u p p l y

-Vcc

GND

R/W

LCDE

R/ W si g nal f ro m th e M PU , wh i ch wheth er t he M PU wants to W RITE

a c t i v e h i g h e n a b l e s i g n a l f r o m t h e d e c o d e r , v i a i n v e r t o r j

t e l l s t h e L C D c o n t r o l l e r

to, or, READ from, the LCM.

of IC7, and a blocking diode, Dl and pull-up resistor, R2 ^

w h i c h c o n v e r t t h e h i gh v ol t a ge o ut p u t f r om I C5 , w h ic h i s

c o n n e c t e d d i r e c t l y t o t h e b a t t e r y , t o n o r m a l T T L l e v e l s .

o / p f r o m t h e L C M t o i n d i c a t e t o t h e M P U t h a t i t i s r e a d y t o

re c i e v e da t a a n d/ o r c o mm a n d s .

A l l d a t a a n d c o m m a n d s fo r t h e L C M f r o m th e M P U , a r e s e n t i n 4 - b i t

n i b b l e s , v i a t h e u p p e r f o u r d a t a l i n e s , D 5 t o D 7 , i n a t w o - b y t e

C o m m a n d s ' a r e w r i t t e n t o l o c a t i o n $ 8 0 0 0 , w h i c h a c c e s s a w r i t e o n l y

r e g i s t e r , w h i l e d a t a i s w r i t t e n a n d r e a d a t $ 8 0 0 1 .

A l l d a t a f or t h e o p e r at i o n o f t h e d i s p la y i s s a v e d a n d u pd a t e d i n t h e

L C D c o n t r o l l e r I C . T h e M P U o n l y w r i t e s d a t a w h e n i t w a n t s t o u p d a t e

t h e d i s p l a y c o n t e n t s .

i™i

0St

fP>

-11-

MODEM

T h e m o d e m , I C 9 T C M 3 1 0 1 , i s a n I C w h i c h b a s i c a l l y c o n v e r t s d i g i t a l s i g n a l s

t o a n a l o ge s i g n a l s a n d v i c e - v e r sa . T h e r e a s o n i s s u c h t h a t d i g i t a l

i n f o r m a t i o n f r o m t h e M P U c a n b e t r a n s f o r m e d i n t o a s i g n a l w h i c h c a n b e t r an s m i t t e d o v e r t he t e le p h o n e n e t w o rk . B ec a u s e o f t h e c h ar a c t er i s t ic s o f t h e t e l e p h o n e s y s t e m , t h e d i g i t a l s i g n a l s a r e c o n v e r t e d t o a u d i o s i g n a l s ,

w i t h t h e t w o d i f f e r e n t d i g i t a l s t a t e s r e p r e s e n t e d b y t w o d i f f e r e n t

f r e q u en c i e s . T h i s s y s t e m i s c a l l e d F r eq u e n c y S h i f t K e y i n g . T h e m o d e m i n t h e P X 1 0 0 0 i s u s e d i n s i m p l e x m o d e , i . e i t i s e it h e r t r a n s m i t t i n g o r

r e c e i v i n g . I n t r a n s m i t m o d e , d i g i t a l d a t a f r o m t h e M P U o / p , P 1 4 , i s f e d

t o t he m o de m T r a n sm it D i gi ta l I /P o n p i n 1 4 . T h e d a t a i s i n t e r n a l l y

converted to a sine wave signal on the Transmit Analogue O/P, pin 11. This

s i g n a l i s 1 . 6 V p - p , a n d h a s a f r e q ue n c y o f 1 7 0 0 H z f o r a ' 0 ' i / p , a n d 1 3 0 0

H z f o r a ' 1 ' i / p . I n r e c e i v e m o d e , a n a u d i o s i g n a l a p p e a r i n g o n t h e R e c e i ve A n a l o g u e I /P, p in 4 o n t h e m od e m , i s c o n v e r t e d t o a d i g i ta l

signal at Receive Digital o/p, pin 8, and fed to the MPU i/p, P20. The

a u d i o f r e q u e n c i e s a r e d e r i v e d f r o m a c l o c k , m a d e u p f r o m c r y s t a l X T 2 , a n d c a p a ci to r s C 9 a nd C 1 0 . T h e v o lt a g e l ev e l a t t he C a r r i e r D e t ec t L e v el i / p,

pi n 1 0, d e te r m in e s wh a t le v el t h e mo d e m w i 1 1 de t ec t a n an a lo g u e s i g na l

i / p . T h i s l e v e l i s s e t b y t he r es is to r c o m b i na ti on R 1 5 a n d R 1 6 , a n d

d e c ou p l e r c a p a c i to r C I 1 P ot e n t i o m e te r P 2 , i n c o m b i n a t i o n w i t h C 1 2 , a d j u s t s t h e d i s t o r t i o n l e v e l o f t h e r e c e i v e d d a t a , b y v a r y i n g t h e v o l t a g e

l e v el o n t h is p i n . P o w e r t o t h e m o d e m i s c o n t r o l l e d b y T 6 , w h ic h i s t u r n e d

o n b y t h e M P U ou t p u t , P ll , v i a r e sis t o r s R 2 6 an d R 4 0 o nly w h e n t h e m o d e m

i s i n u se . T h i s r e d u c e s o v e r a l l p o w e r c o ns u m p t i o n o f t h e P X . T 6 i s i n t u r n f e d f r om V C C b y a s e p e r a te t r a n s i s t o r T 2 , a nd n o t b y T l , b e c a u s e o f

t h e r a t h e r h i g h c u r r e n t c u r r e n t c o n s u m p ti o n o f t h e m o d e m c i r c u i t . Z e n e r d i o d e , Z 2 , o f v a l u e 5 V 6 , e n s u r e s 5 V t o t h e m o d e m , e v e n t h o u g h t h e b a t t e r y v o l t a g e m a y v a r y. T h i s i s n e c c e s a r y s o t h a t i / p ' s C D L a n d R X B r e m a i n

c o n s t a nt . C a p a c it o r C 8 p ro v i de s p o w e r s u p p l y d e c o up l i ng . T h e f r e q u e n ci es u s e d a r e o f t h e C C I T T S t a n d a r d V 2 3 f o r a b a u d r a t e o f 6 0 0 B d , r e g a r d l e s s o f t h e i / p b a u d r a t e t o t h e m o d e m . T h e d a t a c a n b e i n a n y o f t h r e e d i f f e r e n t s p e e d s : 3 0 0 , 6 0 0 o r 1 2 0 0 b i t s / s .

AUDIO OUTPUT AMPLIFIER

A n a l o g u e o u t p u t f r o m t h e m o d e m I C , i s f e d t h r o u g h a c o m p l e m e n t a r y

!S>

d r i v e r b u f f e r s t a g e , c o n s i s t i n g o f D a r l i n g t o n p a i r s , T 8 a n d T 9 , a n d r e s i s t o r s R 3 1 a n d R 3 2 , b e f o r e b e i n g f e d t o t h e s p e a k e r . T h e s i g n a l

i s a c c o u p l e d v i a c a p a c i t o r s , C 2 0 a n d C 2 1 . R 3 3 v a r i e s t h e a c t u a l

v o l t ag e a c r o s s t h e s pe ak er , a nd s o , t h e o ut pu t v o l u m e l e v el . P o w e r t o t h e o u t p u t a m pl iﬁ e r i s s w i t c h ed w i th t h e m o d em b y t r a n s i st o r

T 7 , v i a r e s i s t o r s R 2 7 a n d R 2 8 .

-12-

AUDIO INPUT AMPLIFIER

Analogue input, picked up on the microphone, is fed ﬁrst to the

limiting circuit D9, D10 and R35, then to the ﬁlter circuit, R34 and

C18, and then to the ﬁrst of two ampliﬁer stages, via ac coupler C17.

The ﬁrst is a transistor invertor type, with gain of 100, set by

r e s i s t o r s R 3 8 a n d R 3 9 . T h e o u t p u t i s a c c o u p l e d b y C 2 5 . J

The second consists of an audio op-amp, IC10 TA7330, with gain of

100, determi ned by feed back circ uit of R30, R 48, C16 a nd C19. The «

ou t p ut from th e o p -amp is a c c o u pled by C 1 4 , t hen lim i ted, by tw o j germanium diodes, D14 and D15, and resistor R47, and ac coupled again by C23. This ensures a maximum i/p signal to the modem of 0.7v p-p,

which i s sp eciﬁed for this I C. Because, the modem is only concerned with the frequency of the signal, J

possible clipping caused by these diodes will not effect performance. I C 1 0 i s p o w e r s u p p l y d e c o u p l e d b y c a p a c i t o r C 1 3 a n d C 1 5 . ^

SERIAL OUTPUT CIRCUIT m

The serial output circuit consists of transistor T5 and resistors R23 R24 and R25.

Serial data is fed from output P24 of the MPU, to the base of PNP

transistor, T5, via R24, such that a '0' on P24 turns on T5, and a '1' turns it off. The emitter of T5 is connected to 5V, and the collector to -5V, via resistor R25. Serial output is taken from the collector

of T5, via current limiting resistor, R26. The effect of the output

circuit is such that a '1' on P24, MPU, gives -5V at the output,

while a *0', gives +5V. These levels are compatible with the RS232C

Standard.

p«l

SERIAL INPUT CIRCUIT

The serial input circuit consists of P23 of the MPU, R4, R11,D6, D7,

and Dll. It is u se d to ind icate to the the MPU, w he th er a n external «

device is ready to receive data from the serial output. It is designed J

for use with other RS232C Standard equipment.

The actual input pin is also used by the 12VDC battery charger. Diode Dll prevents current ﬂow into the serial input circuit when the

charg er is inserte d. Diodes D6 and D7 limit voltage levels on the MPU to within accecptable

limits, even'when RS232C Standard voltages of up to 15V in

m a g n i t u d e a p p e a r a t t h e s e r i a l i n p u t . J Resistor R19 is for current-1imiting, and R4 is a pull-up to VCC. ^ A zero, or negative voltage on the serial input pin, appears as 0 on

P2 3 o f t h e MPU. A + 5V, or posi tive vo ltag e o n t he seri a l inpu t p i n j

appears as a '1' on the MPU.

P"8

■ pn

E - 1 3 -

LED DRIVE CIRCUIT.

The LED is turned by two different methods; either directly under

r control of the MPU, an d/or when th e 12VDC batt ery charger is inserted.

t When being driven by the MPU, the circuit involved consists of MPU

« a n d t h e L E D i t s e l f .

output P17, transistor T4, resistors R20, R21, and R22, diode D13

A '0' on the MPU output turns on T4, giving a high on its collector, which drives the LED on, via cur rent-1imi ting resistor R22. A '1'

-> f r om th e M PU wi ll tur n off t he LED . When the battery charger is inserted, the 12VDC drives the LED,

through the circuit involving T13, D12, R44, R45, and R46. Resistors

R44 and R45 provide bias for transistor T13, turning it on, which

P drives t he LED on v ia current-1imitin g resistor R46. Diodes D 12 and

D13 act as blocking diodes to prevent either one of the LED drive

circ ui ts from i nterfer ence wi th the othe r.

p Bo th ci rcu it s are capa ble o f ope ratin g tog eth er; w hen t hey d o,the L ED

burns brighter because of higher current.

T AUDIO TRANSDUCER

Audio input and output to and from the unit is via an audio transducer

m which acts as both microphone and speaker. Because the unit operates

in simplex mode only, this transducer will either be microphone, or speaker at any one time.

AUDIO INPUT/OUTPUT SOCKET

m Audio s ignals can be i nput and outp ut, to and from the PX directl y,

as well as acoustically, via socket J4. When there is something connected in this socket, the audio transducer is disconnected from

p t h e i / o c i r c u i t r y, a n d s i g n a l s a r e f e d d i r e c t l y f r o m t h e e x t e r n a l

device to these circuits.

* RFI REDUCTION CIRCUITRY

Circuitry is included to reduce the amount of Radio Frequency

m I n t e r f e r e n c e , w h i c h i s a s s o c i a t e d w i t h t h e h i g h r a t e of a c t i v i t y [ around the MPU and on the address and data lines.

Two methods of reduction are used. One is to actually reduce the

amount of noise on the power lines. This is done by the capacitors C26 to C29. The second method is to insert ﬁlters on the input and output

m c o n j u n c t i o n w i t h c h o k e s LI t o L 6 .

signals. These ﬁlters are made up from capacitors CI to C4 in

-14-

D I F F E R E N C E S B E T W E E N H V E R S I O N A N D F V E R S I O N ^

As w ell as t he ma in di ff ere nce s, li ste d b elo w, th ere are a few m ino r «

di ffe ren ces al s o :-

Some circuitry which is in discrete component form in version F is on the Hybrid on version H. «|

The number i n g o f cer t a i n c o m p o n e n t s d i ffer s bet w e e n b o t h ve r s i o n s . J

Because of this, unless otherwise stated, the component numbers

m e n t i o n e d b e l o w , r e f e r t o t h e s c h e m a t i c f o r v e r s i o n F . < m

1. On the F version IC10, the audio input op-ampliﬁer chip, is

a M51304L. Its operaton is similar to IC10, (TA7330P), on the H version, except that its output is limited by an AGC (Automatic Gain

Control), instead of the germanium diodes as used in the H version.

2. On version F, the CDL level input to the Modem, IC9, is set by potentiometer, instead of resistor divider, as on version H.

3. On Version F, the voltage sensor, IC8 is excluded. The battery

charge rate is constant, at 25mA, set by resistors R18 and R37 in series. Transistor T3 is always turned on by pull-up resistor, R16

s o R 1 7 i s s h o r t e d o u t . ' ^

4. The 12VDC supply drives the LED via zener diode from cathode D8,

o f 6 V 2 , a n d c u r r e n t - 1 i m i t i n g r e s i s t o r . ^

5. There is no resistor from RAM VDD to ground, in version F. On the

H board this resistor ensures that diodes D3 and D4 are full biased,

making the supply voltage for the RAM closer to speciﬁcation.

6. The RFI reduction circuitry, involving capacitors C26 to C29, is not included in the F version.

^■^

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CHAPTER 3

-16-

SERVICE

3.1 DISASSEMBLY OF PX1000

The PX1000 can be dismantled, for repair and adjustment purposes, as

f o l l o w s : •

1. Remove bottom housing by ﬁrst unscrewing the six self-tap cross-head screws, on the underneath side of the unit. Separate

the bottom housing from the remainder of the unit, by ﬁrst lifting the end nearest the audio socket, J4, and then sliding the other

end from around the power socket, J3.

2. Disconnect the battery pack/speaker from the main circuit by slipping socket J5 from plug J5, on the logic board. The battery

pack is ﬁxed to the bottom housing with adhesive, but can be easily removed for replacement purposes. The speaker sits in a

groove in the rubber sealing ring, and be eased out with the aid

of a small ﬂat top screwdriver or similar tool. Desolder the wires

from the speaker to seperate it completely from the unit.

T h e r u b b e r a c c o u s t i c s e a l i n g ri n g c a n be r e m o v e d b y s l i p p i n g i t ^

through the hole in the housing. J

(553'

(5*jj

3. Remove the logic board from the keyboard/LCM assembly by separating m 32-pin socket Jl, on the logic board from the 32-pin plug Jl, on

the keyboard PCB, using a small ﬂat-head screw-driver.

4. To ac cess th e LCD m odu le, ﬁ rs t rem ove t he i nst ructi on st icker f rom 1 the LCD cover. Unscrew the nine cross-head screws, and remove the "

LCD cover. To separate the LCD module from the keyboard PCB, desolder the ten "1

c o n t a c t s o f t h e ﬂ e x i - P C B f r o m t h e L C M P C B . )

5 . To a c c e s s th e r u b b e r k e y - p a d an d ke y s , s n i p t h e t o p s o f f t h e * *■■

plastic pillars which hold the keyboard PCB to the unit, and lift off the keyboard PCB. Replace the PCB by melting down the* pillars

o v e r t h e P C B h o l e s . ( B e c a u s e t h e p i l l a r s g e t sm a l l e r e a c h t i m e , «

this cannot be done too often.)

The ﬂexi-PCB can be separated from the keyboard PCB by desoldering '

the ten contacts, as with the LCM PCB. To remove the ﬂexi-PCB

fro m th e un i t co m p l e t e ly, it mus t ﬁr s t be be n t ov e r, a n d th e n s l i d R through the hinge.

Bill

-17-

3.2 CALIBRATION ADJUSTMENTS

T he o n l y a d ju s t m e n t s wh i c h n e e d to b e d o n e on t h e P X 1 00 0 a r e t o tw o

p o t e n t i o m e t e r s o n t h e l o g i c b o a r d . T h e s e a d j u s t m e n t s a r e d o n e b e f o re

t h e u n i t l e a v e s t h e f a c t o r y, b u t m a y , i n s o m e c a se s , n e e d t o b e r e do n e because of slipping of the setting due to vibration etc.

T h e t w o p o t s , t o b e a d j u s t e d a r e d i f f e r e n t d e pe n d in g o n w h e t h e r t h e

b o a r d i s a n F o r H v e r s i o n . To a d j u s t b o t h , ﬁ r s t r e m o v e t h e b o t t o m hous ing.

P o t . P 2 s e r v e s a s i m i l a r f u n c t i o n o n b o t h b o a r d s . I t s p u r p o s e i s t o m i n i m i s e t h e d i s t o r t i o n o n t h e r e c e i v e d m o d e m s i g n a l . To a d j u s t t h i s ,

e i t h e r d i r e c t l y o r a c c o u s t i c a l c o u p l e a n o t h e r P X t o t h e u n i t . P r e s s

O N/S T O P + D o n t h e o t h e r uni t . P r e s s R C V E on t h e u n i t t o be a d j u s t e d . Place the probe of an oscilloscope on pin 8 of IC1. A square wave

T T L s i g n a l o f 1 2 0 0 B d s h o u l d a p p e a r o n t h e s c o p e s c r e e n . A d j u s t

p o t e n t i o m e t e r P 2 , s u c h t h a t t h e m a r k / s p a c e r a t i o o f t h i s s i g n a l i s equal.

P o t . P I o n l o g i c b o a r d F i s u s e d t o s e t t h e C D L ( c a r r i e r d e t e c t l e v e l )

o n t h e m o d e m I C . T h i s p o t . s h o u l d b e a d j u s t e d s u c h t h a t t h e v o l t a g e

level appearing on pin 10 of the modem, IC9, should be between 0.64

a nd 0 . 7 4 t i m e s th e v o l t a g e V DD a t p i n 1 o f t h e m o d e m .

T h i s p o t . i s r e p l a c e d b y a r e s i s t o r d i v i d e r n e t w o r k o n t h e H v e r s i o n

l o g i c b o a r d.

O n l o g i c b o a r d H , p o t . P I i s u s e d t o a d j u s t t h e l e v e l a t w h i c h t h e

b a t t e r y c h ar g e c u r re nt r a te c h an ge s f ro m h i g h t o l o w .

To ﬁ x t h i s , ﬁ r s t c o n n e c t a v a r i a b l e v o l t a g e s u p p l y t o c o n n e c t o r

J 5 o n t h e l o g i c b o a r d i n s t e a d o f t h e b a t t e r y t e r m i n a l s . P l a c e a

v o l t m e t e r a c c r o s s t h i s s u p p l y . P l a c e e i t h e r a n o s c i l l o s c o p e o r s e c o n d

v o l t m e t e r a t p i n 1 o f I C 8 .

IP1

Tu r n o n t he u n i t , a n d k e e p i t o n b y p e s s i n g O N / S T O P + D .

I n cr e a s e t h e v o l t a g e s u c h t h a t 7 . 4 5 V a p p ea r s o n t h e ﬁ r st m e te r.

S e t P I t o m a x im u m a n t i - c lo ck w i se p os it io n . N o w t u rn P I c l o ck w i se

u n ti l t h e v o l t a g e l e v e l o n t h e p i n 1 , I C 8 g o e s l o w . R e d u c e v o l t a g e o n t h e p ow er s up p l y t o a b o u t 6 . 5 V, a n d t h en i nc re a s e s l ow ly u nt i l

t h e v ol t ag e a t p i n 1 , I C 8 g o e s l o w. T h e r e a d i n g o n t h e ﬁ r s t m e t e r sh ou l d n ow b e be tw ee n 7. 4 V a n d 7 .5 V.

T h i s p o t . i s n o t p r e s e n t o n t h e F v er s i o n l o g i c b o a r d a s I C 8 i s n o t

included in the circuit.

+ 43 hidden pages

Text Tell PXP40, PX-1000 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual