
2007-2012 Microchip Technology Inc.
DS39778E-page 67
PIC18F87J11 FAMILY
6.0
MEMORY ORGANIZATION
There are two types of memory in PIC18 Flash
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.
Additional detailed information on the operation of the
6.1
Program Memory Organization
PIC18 microcontrollers implement a 21-bit Program
Counter (PC) 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 entire PIC18F87J11 family of devices offers three
different on-chip Flash program memory sizes, from
64 Kbytes (up to 16,384 single-word instructions) to
128 Kbytes (65,536 single-word instructions). The
program memory maps for individual family members
FIGURE 6-1:
MEMORY MAPS FOR PIC18F87J11 FAMILY DEVICES
Note:
Sizes of memory areas are not to scale. Sizes of program memory areas are enhanced to show detail.
Unimplemented
Read as ‘0’
Unimplemented
Read as ‘0’
000000h
1FFFFFF
PIC18FX6J11
PIC18FX6J16
PIC18FX7J11
00FFFFh
017FFFh
PC<20:0>
Stack Level 1
Stack Level 31
CALL, CALLW, RCALL,
RETURN, RETFIE, RETLW,
21
Us
er
M
e
mo
ry
S
pace
On-Chip
Memory
On-Chip
Memory
On-Chip
Memory
ADDULNK, SUBULNK
Config. Words
01FFFFh
Unimplemented
Read as ‘0’