HT9480 datasheet(7/47 Pages) HOLTEK

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HT9480

Rev. 1.20

July 31, 2002

Program memory

- ROM

The program memory (ROM) is used to store the pro-

gram instructions that are to be executed. It consists of

data, table(s), and interrupt entries, and is organized

into 8192

´16 bits, which are addressed by the PC and ta-

ble pointer.

Certain locations in the ROM are reserved for specific

usage:

· Location 0000H

Location 0000H is reserved for program initialization.

The program always begins execution at this location

each time the chip is reset.

· Location 0004H

Location 0004H is reserved for the data ready inter-

rupt and battery fail interrupt service programs. If an

interrupt results from a pager decoder interrupt re-

quest or from a battery fail interrupt request, and the

interrupt is enabled, and the stack is not full, the pro-

gram begins execution at location 0004H. The occur-

rence of a data ready interrupt or a battery fail interrupt

is detected by checking the battery fail interrupt bit

(1EH-bit 4, BF flag) and the data ready interrupt bit

(1EH-bit 7, DR flag). The interrupt should be carefully

processed if both interrupt bits are active.

· Location 0008H

Location 0008H is reserved for the programmable

timer interrupt service program. If an interrupt results

from a programmable timer interrupt request (its

source is from 256Hz divided by N, where the value of

N ranges from 1 to 256.), and the interrupt is enabled,

and the stack is not full, the program begins execution

at location 0008H.

· Location 000CH

Location 000CH is reserved for the timer/event counter

interrupt service program. If a timer interrupt results from

a timer/event counter overflow, and the interrupt is en-

abled, and the stack is not full, the program begins exe-

cution at location 000CH.

· Look-up tables XX00H~XXFFH

The ROM is composed of 32 groups (each group con-

tains 256 continuous words) which can be used as

look up tables. The instructions

²TABRDC [m]² (the

current table) and

²TABRDL [m]² (the last table) trans-

fer the contents of the low-order byte to the specified

data memory, and the contents of the high-order byte

to TBLH (Table High-order Byte Register) (08H). Only

the destination of the low-order byte in the table is

well-defined, the other bits of the table word are all

transferred to the low portion of TBLH. TBLH is read

only while the table pointer (TBLP) is a read-

able/writable register (07H) used to indicate the table

location. Before accessing the table, the location

should be placed in TBLP. All of the table related in-

structions require 2 cycles to complete the operation.

This feature is efficient only for the movement of the

blocks, which may function as look-up tables or as a

normal program memory depending upon the require-

ments.

Stack register

- STACK

The stack register is a special memory port used to save

the contents of the PC. It is divided into 8 levels. The

stack register is neither part of the data nor part of the

program, and is neither readable nor writable. The acti-

vated level of the stack register is indexed by the stack

pointer (SP), and is neither readable nor writable. At the

commencement of a subroutine call or an interrupt ac-

knowledge, the contents of the PC is pushed onto the

stack. At the end of the subroutine or the interrupt rou-

tine, as signaled by a return instruction (RET or RETI),

the content s of the PC is restored to its previous value

from the stack. After a chip reset, the SP will point to the

top of the stack.

0 0 0 H

0 0 4 H

0 0 8 H

D e v i c e i n i t i a l i z a t i o n p r o g r a m

D a t a r e a d y i n t e r r u p t & b a t t e r y

f a i l i n t e r r u p t s u b r o u t i n e

T i m e r / e v e n t c o u n t e r i n t e r r u p t s u b r o u t i n e

P r o g r a m

R O M

1 6 b i t s

0 1 0 H

1 . . . H

P r o g r a m m a b l e t i m e r i n t e r r u p t s u b r o u t i n e

0 0 C H

Program memory

Instruction(s)

Table Location

*12

*11

*10

TABRDC [m]

P12

P11

P10

TABRDL [m]

1111

Note: *12~*0: Table location bits

P12~P8: Current program counter bits

@7~@0: Table pointer bits

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