PIC18F2420 MICROCHIP [Microchip Technology], PIC18F2420 Datasheet - Page 55

• Manufacturer Part Number: PIC18F2420
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

5.0
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 concur-
rent 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 is
discussed separately in Section 7.0 “Data EEPROM
Memory”.
FIGURE 5-1:
 2004 Microchip Technology Inc.
MEMORY ORGANIZATION
PROGRAM MEMORY MAP AND STACK FOR
PIC18F2420/2520/4420/4520 DEVICES
CALL,RCALL,RETURN
RETFIE,RETLW
Program Memory
PIC18FX4X0
Read ‘0’
On-Chip
High Priority Interrupt Vector
Low Priority Interrupt Vector
Stack Level 31
3FFFh
4000h
Stack Level 1
Reset Vector
PIC18F2420/2520/4420/4520
PC<20:0>
Preliminary
Program Memory
PIC18FX5X0
On-Chip
Read ‘0’
5.1
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 PIC18F2420 and PIC18F4420 each have
16 Kbytes of Flash memory and can store up to 8,192
single-word
PIC18F4520 each have 32 Kbytes of Flash memory
and can store up to 16,384 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 map for PIC18F2420/2520/
4420/4520 devices is shown in Figure 5-1.
7FFFh
8000h
0000h
0008h
0018h
1FFFFFh
200000h
Program Memory Organization
21
instructions.
The
PIC18F2520
DS39631A-page 53
and