PIC18LF4331-ESLASHML datasheet(61/392 Pages) MICROCHIP

61 / 392 page

 2010 Microchip Technology Inc.

DS39616D-page 61

PIC18F2331/2431/4331/4431

6.0

MEMORY ORGANIZATION

There are three memory types in enhanced MCU

devices. These memory types are:

• Program Memory

• Data RAM

• Data EEPROM

As Harvard architecture devices, the data and program

memories use separate buses, enabling concurrent

access of the two memory spaces. The data EEPROM,

for practical purposes, can be regarded as a peripheral

device, since it is addressed and accessed through a

set of control registers.

Additional detailed information on the operation of the

Flash program memory is provided in Section 8.0

“Flash

Program

Memory”

. Data EEPROM is

discussed separately in Section 7.0 “Data EEPROM

Memory”

FIGURE 6-1:

PROGRAM MEMORY MAP

AND STACK FOR

PIC18F2331/4331

6.1

Program Memory Organization

PIC18 microcontrollers implement a 21-bit program

counter that can address a 2-Mbyte program memory

space. Accessing a location between the upper bound-

ary of the physically implemented memory and the

2-Mbyte address will return all ‘0’s (a NOP instruction).

The PIC18F2331/4331 devices each have 8 Kbytes of

Flash memory and can store up to 4,096 single-word

instructions.

The PIC18F2431/4431 devices each have 16 Kbytes

of Flash memory and can store up to 8,192 single-word

instructions.

PIC18 devices have two interrupt vectors. The Reset

vector address is at 000000h and the interrupt vector

addresses are at 000008h and 000018h.

The program memory maps for PIC18F2331/4331 and

PIC18F2431/4431 devices are shown in Figure 6-1

and Figure 6-2, respectively.

FIGURE 6-2:

PROGRAM MEMORY MAP

AND STACK FOR

PIC18F2431/4431

PC<20:0>

Stack Level 1



Stack Level 31

Reset Vector LSb

High-Priority Interrupt Vector LSb



CALL,RCALL,RETURN

RETFIE,RETLW

000000h

000008h

000018h

1FFFFFh

Low-Priority Interrupt Vector LSb

On-Chip Flash

Program Memory

002000h

001FFFh

Unused

Read ‘0’s

PC<20:0>

Stack Level 1



Stack Level 31

Reset Vector LSb

High-Priority Interrupt Vector LSb



CALL,RCALL,RETURN

RETFIE,RETLW

000000h

000008h

000018h

1FFFFFh

Low-Priority Interrupt Vector LSb

On-Chip Flash

Program Memory

004000h

003FFFh

Unused

Read ‘0’s

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