HT48C50- datasheet(8/45 Pages) HOLTEK

8 / 45 page

HT48C50-1

June 14, 2000

Preliminary

The lower byte of the program counter (PCL) is

a readable and writeable register (06H).

Moving data into the PCL performs a short

jump. The destination will be within 256 loca-

tions.

When a control transfer takes place, an addi-

tional dummy cycle is required.

Program memory - ROM

The program memory is used to store the pro-

gram instructions which are to be executed. It

also contains data, table, and interrupt entries,

and is organized into 4096´15 bits, addressed

by the program counter and table pointer.

Certain locations in the program memory are

reserved for special usage:

· Location 000H

This area is reserved for program initializa-

tion. After chip reset, the program always be-

gins execution at location 000H.

· Location 004H

This area is reserved for the external inter-

rupt service program. If the INT input pin is

activated, the interrupt is enabled and the

stack is not full, the program begins execution

at location 004H.

· Location 008H

This area is reserved for the timer/event coun-

ter 0 interrupt service program. If a timer inter-

rupt results from a timer/event counter 0

overflow, and if the interrupt is enabled and the

stack is not full, the program begins execution

at location 008H .

Mode

Program Counter

*11 *10

Initial Reset

000000000000

External Interrupt

000000000100

Timer/Event Counter 0

Overflow

000000001000

Timer/Event Counter 1

Overflow

000000001100

Skip

PC+2

Loading PCL

*11 *10

Jump, Call Branch

#11 #10

Return from Subroutine

S11 S10 S9

Program counter

Note: *11~*0: Program counter bits

S11~S0: Stack register bits

#11~#0: Instruction code bits

@7~@0: PCL bits

15 b i t s

FFF H

nFFH

P r ogr am

Me m o r y

D e vi ce I ni t i a l i za t i o n P r o g r a m

E x te r n a l Inte r r u p t S u b r o u ti ne

T i m e r / E v ent C ount e r 0

I nt e r r upt S ubr out i ne

Look - up T abl e ( 256 w o r d s )

N o t e : n r anges f r o m 0 t o F

00C H

n00H

008H

004H

000H

T i m e r / E v ent C ount e r 1

I nt e r r upt S ubr out i ne

Program memory

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