PIC18F2450/4450
5.1
Program Memory Organization
5.0
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
NOPinstruction).
There are two types of memory in PIC18F2450/4450
microcontroller devices:
• Program Memory
• Data RAM
As Harvard architecture devices, the data and program
memories use separate busses; this allows for
concurrent access of the two memory spaces.
The PIC18F2450 and PIC18F4450 each have 16 Kbytes
of Flash memory and can store up to 8192 single-word
instructions.
Additional detailed information on the operation of the
Flash program memory is provided in Section 6.0
“Flash Program Memory”.
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 PIC18F2450 and
PIC18F4450 devices are shown in Figure 5-1.
FIGURE 5-1:
PROGRAM MEMORY MAP AND STACK FOR PIC18F2450/4450 DEVICES
PIC18F2450/4450
PC<20:0>
21
CALL, RCALL, RETURN,
RETFIE, RETLW, CALLW,
ADDULNK, SUBULNK
Stack Level 1
•
•
•
Stack Level 31
Reset Vector
0000h
0008h
High Priority Interrupt Vector
Low Priority Interrupt Vector 0018h
On-Chip
Program Memory
3FFFh
4000h
Read ‘0’
1FFFFFh
200000h
© 2006 Microchip Technology Inc.
Advance Information
DS39760A-page 53
MICROCHIP [ MICROCHIP ]
