Техническая Спецификация для Microchip Technology ARD00385

DS39957D-page 86

 2009-2011 Microchip Technology Inc.

PIC18 microcontrollers implement a 21-bit Program
Counter that 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 entire PIC18F87K90 family offers a range of
on-chip Flash program memory sizes, from 32 Kbytes
(up to 16,384 single-word instructions) to 128 Kbytes
(65,536 single-word instructions).
• PIC18F65K90 and PIC18F85K90 – 32 Kbytes of 

Flash memory, storing up to 16,384 single-word 
instructions

• PIC18F66K90 and PIC18F86K90 – 64 Kbytes of 

Flash memory, storing up to 32,768 single-word 
instructions

• PIC18F67K90 and PIC18F87K90 – 128 Kbytes of 

Flash memory, storing up to 65,536 single-word 
instructions

The program memory maps for individual family
members are shown in 

6.1.1

HARD MEMORY VECTORS

All PIC18 devices have a total of three hard-coded
return vectors in their program memory space. The
Reset vector address is the default value to which the
Program Counter returns on all device Resets; it is
located at 0000h.
PIC18 devices also have two interrupt vector
addresses for handling high-priority and low-priority
interrupts. The high-priority interrupt vector is located at
0008h and the low-priority interrupt vector is at 0018h.
The locations of these vectors are shown, in relation to
the program memory map, in 

.

Reset Vector

Low-Priority Interrupt Vector

0000h

0018h

On-Chip

Program Memory

High-Priority Interrupt Vector

0008h

1FFFFFh

Read ‘0’

(Top of Memory) represents upper boundary 
of on-chip program memory space (see 

 for device-specific values). 

Shaded area represents unimplemented 
memory. Areas are not shown to scale.