Datasheet

dsPIC33FJ32GS406/606/608/610 and dsPIC33FJ64GS406/606/608/610
DS70591E-page 46  2009-2012 Microchip Technology Inc.
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 (see
Figure 4-2).
Program memory addresses are always word-aligned
on the lower word, and addresses are incremented or
decremented by two during the 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 dsPIC33FJ32GS406/606/608/610 and
dsPIC33FJ64GS406/606/608/610 devices reserve the
addresses between 0x00000 and 0x000200 for
hard-coded program execution vectors. 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.
The dsPIC33FJ32GS406/606/608/610 and
dsPIC33FJ64GS406/606/608/610 devices also have
two Interrupt Vector Tables (IVT), 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 discussion of the
Interrupt Vector Tables is provided in Section 7.1
“Interrupt Vector Table”.
FIGURE 4-2: PROGRAM MEMORY ORGANIZATION
0816
PC Address
0x000000
0x000002
0x000004
0x000006
23
00000000
00000000
00000000
00000000
Program Memory
‘Phantom’ Byte
(read as ‘0’)
least significant word
most significant word
Instruction Width
0x000001
0x000003
0x000005
0x000007
msw
Address (lsw Address)