PIC18F4685-ISLASHSP datasheet(63/484 Pages) MICROCHIP

63 / 484 page

Preliminary

DS39761B-page 61

PIC18F2682/2685/4682/4685

5.0

MEMORY ORGANIZATION

There are three types of memory in PIC18 Enhanced

microcontroller devices:

• Program Memory

• Data RAM

• Data EEPROM

As Harvard architecture devices, the data and program

memories use separate busses; this allows for

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 6.0

“Flash

Program

Memory”.

Data

EEPROM

discussed separately in Section 7.0 “Data EEPROM

Memory”.

5.1

Program Memory Organization

PIC18 microcontrollers implement a 21-bit program

counter, which is capable of addressing a 2-Mbyte

program memory space. Accessing a location between

the upper boundary of the physically implemented

memory and the 2-Mbyte address will return all ‘0’s (a

NOP

instruction).

The PIC18F2682 and PIC18F4682 each have 80 Kbytes

of Flash memory and can store up to 40,960 single-word

instructions. The PIC18F2685 and PIC18F4685 each

have 96 Kbytes of Flash memory and can store up to

49,152 single-word instructions.

PIC18 devices have two interrupt vectors. The Reset

vector address is at 0000h and the interrupt vector

addresses are at 0008h and 0018h.

The program memory maps for PIC18F2682/4682 and

PIC18F2685/4685 devices are shown in Figure 5-1.

FIGURE 5-1:

PROGRAM MEMORY MAP AND STACK FOR PIC18F2682/2685/4682/4685 DEVICES

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 00008h

1FFFFFh

14000h

13FFFh

Read ‘0’

200000h

PC<20:0>

Stack Level 1

•

Stack Level 31

Reset Vector

Low Priority Interrupt Vector

•

CALL, RCALL, RETURN

RETFIE, RETLW

0000h

0018h

18000h

17FFFh

On-Chip

Program Memory

High Priority Interrupt Vector 0008h

Read ‘0’

1FFFFFh

200000h

PIC18F2682/4682

PIC18F2685/4685

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