PIC24FJ16MC101_12 Datasheet, PDF (33/350 Pages) Microchip Technology – 16-bit Microcontrollers (up to 32 KB Flash and 2 KB SRAM)

PIC24FJ16MC101/102 AND PIC24FJ32MC101/102/104
4.1.1
PROGRAM MEMORY
ORGANIZATION
The program memory space is organized in word-
addressable blocks. Although it is treated as 24 bits
wide, it is more appropriate to think of each address of
the program memory as a lower and upper word, with
the upper byte of the upper word being unimplemented.
The lower word always has an even address, while the
upper word has an odd address (Figure 4-3).
Program memory addresses are always word-aligned
on the lower word, and addresses are incremented or
decremented by two during code execution. This
arrangement provides compatibility with data memory
space addressing and makes data in the program
memory space accessible.
4.1.2 INTERRUPT AND TRAP VECTORS
All PIC24FJ16MC101/102 and PIC24FJ32MC101/102/
104 devices reserve the addresses between 0x00000
and 0x000200 for hard-coded program execution vec-
tors. A hardware Reset vector is provided to redirect
code execution from the default value of the PC on
device Reset to the actual start of code. A GOTO
instruction is programmed by the user application at
0x000000, with the actual address for the start of code
at 0x000002.
PIC24FJ16MC101/102 and PIC24FJ32MC101/102/
104 devices also have two interrupt vector tables,
located from 0x000004 to 0x0000FF and 0x000100 to
0x0001FF. These vector tables allow each of the
device interrupt sources to be handled by separate
Interrupt Service Routines (ISRs). A more detailed dis-
cussion of the interrupt vector tables is provided in
Section 7.1 “Interrupt Vector Table”.
FIGURE 4-3:
PROGRAM MEMORY ORGANIZATION
msw
Address
0x000001
0x000003
0x000005
0x000007
most significant word (msw)
23
16
00000000
00000000
00000000
00000000
least significant word (lsw)
8
PC Address
(lsw Address)
0
0x000000
0x000002
0x000004
0x000006
Program Memory
‘Phantom’ Byte
(read as ‘0’)
Instruction Width
© 2011-2012 Microchip Technology Inc.
Preliminary
DS39997C-page 33