HT9480 datasheet(8/47 Pages) HOLTEK

8 / 47 page

HT9480

Rev. 1.20

July 31, 2002

If the stack is full and a non-masked interrupt occurs, the

interrupt request flag is recorded but acknowledging is

inhibited until the value of the SP is decremented (by

RET or RETI), allowing that interrupt to be serviced. As

this feature can prevent a stack overflow, the use of the

structure becomes much easier. In a similar case, if the

stack is full, and a

²CALL² is subsequently executed, a

stack overflow occurs and the first entry is lost (only the

most recent eight return addresses are stored).

Data memory

- RAM

The data memory (RAM) is designed in three banks, i.e.,

bank 0, bank 1, and bank 27, and comprised of four

functional groups, namely special function registers (of

´8 bits; 1´4 bit; 1´2 bit in bank0), data memory (of

416

´8 bits; 224´8 in bank 0; 192´8 in bank 1), LCD dis-

play mapping memory (of 35

´4 bits), and decoder con-

figuration RAM mapping memory (of 21

´8 bits). Most of

the these groups are readable/writable but some are

read only.

: U n u s e d , r e a d a s " 0 0 "

B A N K 0

B A N K 1

2 0 H

. . H

M P 0

B P

A C C

P C L

T B L P

T B L H

S T A T U S

I N T C

T M R 1

T M R C 1

P A

P B

P B C

P C

W D T S

3 . H

4 0 H

M P 1

I A R 1

I A R 0

D e c o d e r c o n t r o l / f l a g

D e c o d e r d a t a

T o n e c o n t r o l

G e n e r a l p u r p o s e

D A T A M e m o r y

( 1 9 2 B y t e s )

1 . H

1 E H

1 D H

1 C H

1 B H

1 A H

1 9 H

1 8 H

1 7 H

1 6 H

1 5 H

1 4 H

1 3 H

1 2 H

1 1 H

1 0 H

0 . H

0 E H

0 D H

0 C H

0 B H

0 A H

0 9 H

0 8 H

0 7 H

0 6 H

0 5 H

0 4 H

0 3 H

0 2 H

0 1 H

0 0 H

T M R 0

T M R C 0

B A N K 2 7

4 0 H

E 2 H

. . H

L C D D i s p l a y

M a p p i n g

( 3 5 X 4 B i t s )

3 . H

0 0 H

D e c o d e r c o n f i g u r a t i o n

M e m o r y ( 2 1 B y t e s )

5 4 H

C 0 H

G e n e r a l p u r p o s e

D A T A M e m o r y

( 1 9 2 B y t e s )

G l o b a l D A T A

M e m o r y

( 3 2 B y t e s )

P C C

RAM mapping

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