GMS81C7008 datasheet(25/123 Pages) HYNIX

25 / 123 page

GMS81C7008/7016

APR., 2001 Ver 2.01

8.2 Program Memory

A 16-bit program counter is capable of addressing up to 64K

bytes, but this device has 8K/16K bytes program memory space

only physically implemented. Accessing 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 ad-

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

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

Program Memory. Program Memory area contains the user pro-

gram.

Figure 8-5 Program Memory Map

Page Call (PCALL) area contains subroutine program to reduce

program byte length by using 2 bytes PCALL instead 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 ad-

dress, 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 location 0FFFAH. The in-

terrupt service locations spaces 2-byte interval: 0FFF8H and

0FFF9H for External Interrupt 1, 0FFFAH and 0FFFBH for Exter-

nal 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 Mem-

ory.

Figure 8-6 Interrupt Vector Area

Interrupt

Vector Area

C000H

FEFFH

FF00H

FFC0H

FFDFH

FFE0H

FFFFH

E000H

TCALL area

0FFE0H

Address

Vector Area Memory

Timer/Counter 3

Timer/Counter 2

Watch Timer

A/D Converter

External Interrupt 0

Timer/Counter 1

Basic Interval Timer

Key Scan

RESET

Watchdog Timer

Serial Peripheral Interface

“-” means reserved area.

NOTE:

External Interrupt 2

External Interrupt 1

Timer/Counter 0

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