4.0 MEMORY ORGANIZATION
There are two memory blocks in Enhanced MCU
devices. These memory blocks are:
• Program Memory
• Data Memory
Each block has its own bus so that concurrent access
can occur.
4.1 Program Memory Organization
The PIC18CXX8 devices have a 21-bit program
counter that is capable of addressing the 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
shows the diagram for program memory map and stack
for the PIC18C658 and PIC18C858.
4.1.1 INTERNAL PROGRAM MEMORY
OPERATION
All devices have 32 Kbytes of internal EPROM program
memory. This means that the PIC18CXX8 devices can
store up to 16K of single word instructions. Accessing
a location between the physically implemented mem-
ory and the 2 Mbyte address will cause a read of all '0's
(a NOP instruction).
PIC18CXX8
FIGURE 4-1:
PROGRAM MEMORY MAP
AND STACK FOR
PIC18C658/858
PC<20:0>
21
Stack Level 1
•
••
Stack Level 31
RESET Vector
0000h
High Priority Interrupt Vector 0008h
Low Priority Interrupt Vector 0018h
On-chip
Program Memory
7FFFh
8000h
Read ’1’
1FFFFFh
2000 Microchip Technology Inc.
Advanced Information
DS30475A-page 41