PIC18F258 datasheet(39/384 Pages) MICROCHIP

39 / 384 page

 2002 Microchip Technology Inc.

Preliminary

DS41159B-page 37

PIC18FXX8

4.0

MEMORY ORGANIZATION

There are three memory blocks in Enhanced MCU

devices. These memory blocks are:

• Enhanced FLASH Program Memory

• Data Memory

• EEPROM Data Memory

Data and program memory use separate busses,

which allows concurrent access of these blocks. Addi-

tional detailed information on Data EEPROM and

FLASH program memory is provided in Section 5.0 and

Section 6.0, respectively.

4.1

Program Memory Organization

The PIC18F258/458 devices have a 21-bit program

counter that is capable of addressing a 2 Mbyte

program memory space.

The RESET vector address is at 0000h and the

interrupt vector addresses are at 0008h and 0018h.

FIGURE 4-1:

PROGRAM MEMORY MAP

AND STACK FOR

PIC18F258/458

Figure 4-1 shows the diagram for program memory

map and stack for the PIC18F258 and PIC18F458.

Figure 4-2 shows the the diagram for the program

memory map and stack for the PIC18F248 and

PIC18F448.

4.1.1

INTERNAL PROGRAM MEMORY

OPERATION

The PIC18F258 and the PIC18F458 have 32 Kbytes of

internal Enhanced FLASH program memory. This

means that the PIC18F258 and the PIC18F458 can

store up to 16K of single word instructions. The

PIC18F248

and

PIC18F448

have

16 Kbytes

Enhanced FLASH program memory. This translates

into 8192 single-word instructions, which can be stored

in the Program memory. Accessing a location between

the physically implemented memory and the 2 Mbyte

address will cause a read of all '0's (a NOP instruction).

FIGURE 4-2:

PROGRAM MEMORY MAP

AND STACK FOR

PIC18F248/448

PC<20:0>

Stack Level 1

•

Stack Level 31

RESET Vector

Low Priority Interrupt Vector

•

CALL,RCALL,RETURN

RETFIE,RETLW

0000h

0018h

8000h

7FFFh

On-Chip

Program Memory

High Priority Interrupt Vector 0008h

Read ’0’

1FFFFFh

200000h

PC<20:0>

Stack Level 1

•

Stack Level 31

RESET Vector

Low Priority Interrupt Vector

•

CALL,RCALL,RETURN

RETFIE,RETLW

0000h

0018h

On-Chip

Program Memory

High Priority Interrupt Vector 0008h

1FFFFFh

4000h

3FFFh

Read ’0’

200000h

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