HMS87C1102 datasheet(27/88 Pages) HYNIX

27 / 88 page

Apr. 2001 ver 1.0

HMS87C130XA/120XA/110XA

8.2 Program Memory

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

64K bytes, but these devices have 4K/2K bytes program

memory space only physically implemented. Accessing a

location above FFFFH will cause a wrap-around to 0000H.

Figure 8-4, 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 8-5.

As shown in Figure 8-4, each area is assigned a fixed loca-

tion in Program Memory. Program Memory area contains

the user program.

Figure 8-4 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 8-6.

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.

As for the area from 0FF00H to 0FFFFH, if any area of

them is not going to be used, its service location is avail-

able as general purpose Program Memory.

Figure 8-5 Interrupt Vector Area

PROGRAM

MEMORY

TCALL

AREA

INTERRUPT

VECTOR AREA

F000H

FEFFH

FF00H

FFC0H

FFDFH

FFE0H

FFFFH

PCALL

AREA

F800H

LDA

TCALL

0FH

;

1BYTE INSTR UCTIO N

INSTEAD O F 3 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

0FFE0H

Address

Vector Area Memory

Basic Interval Interrupt Vector Area

A/D Converter Interrupt Vector Area

Timer/Counter 1 Interrupt Vector Area

Timer/Counter 0 Interrupt Vector Area

External Interrupt 0 Vector Area

RESET Vector Area

External Interrupt 1 Vector Area

Watchdog Timer Interrupt Vector Area

“-” means reserved area.

NOTE:

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