HMS81024E datasheet(22/77 Pages) HYNIX

22 / 77 page

HMS81004E/08E/16E/24E/32E

JUNE 2001 Ver 1.00

8.2 Program Memory

A 16-bit program counter is capable of addressing up to

64K bytes, but this device has 4/8/16/24/32K bytes pro-

gram memory space only physically implemented. Ac-

cessing a location above FFFFH will cause a wrap-around

to 0000H.

Figure 8-5 , shows a map of Program Memory. After reset,

the CPU begins execution from reset vector which is stored

in address FFFEH and FFFFH as shown in Figure 8-6 .

As shown in Figure 8-5 , each area is assigned a fixed lo-

cation in Program Memory. Program Memory area con-

tains the user program.

Figure 8-5 Program Memory Map

Page Call (PCALL) area contains subroutine program to

reduce program byte length by using 2 bytes PCALL in-

stead of 3 bytes CALL instruction. If it is frequently

called, it is more useful to save program byte length.

Table Call (TCALL) causes the CPU to jump to each

TCALL address, where it commences the execution of the

service routine. The Table Call service area spaces 2-byte

for every TCALL: 0FFC0H for TCALL15, 0FFC2H for

TCALL14, etc., as shown in Figure 8-7 .

Example: Usage of TCALL

The interrupt causes the CPU to jump to specific location,

where it commences the execution of the service routine.

The External interrupt 0, for example, is assigned to loca-

tion 0FFFAH. The interrupt service locations spaces 2-byte

interval: 0FFF8H and 0FFF9H for External Interrupt 1,

0FFFAH and 0FFFBH for External Interrupt 0, etc.

Any area from 0FF00H to 0FFFFH, if it is not going to be

used, its service location is available as general purpose

Program Memory.

Figure 8-6 Interrupt Vector Area

TCALL

AREA

INTERRUPT

VECTOR AREA

FF00H

FFC0H

FFE0H

FFFFH

PCALL

AREA

A000H

8000H

F000H

E000H

C000H

LDA

TCALL

0FH

;

1BYTE INSTR UCTIO N

INSTEAD O F 2 BYTES

NO RM AL CALL

;

;TABLE CALL ROUTINE

;

FUNC_A:

LDA

LRG0

RET

;

FUNC_B:

LDA

LRG1

RET

;

;TABLE CALL ADD. AREA

;

ORG

0FFC0H

;

TCALL ADDRESS AREA

FUNC_A

FUNC_B

Address

Vector Area Memory

Basic Interval Timer Interrupt Vector Area

Timer2 Interrupt Vector Area

Timer0 Interrupt Vector Area

External Interrupt 2 Vector Area

Key Scan Interrupt Vector Area

RESET Vector Area

External Interrupt 1 Vector Area

Timer1 Interrupt Vector Area

Watch Dog Timer Interrupt Vector Area

"-" means reserved area.

NOTE:

0FFDEH

S/W Interrupt Vector Area

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