70291E Datasheet, PDF (40/436 Pages) Microchip Technology – High-Performance, 16-bit Digital Signal Controllers

dsPIC33FJ32MC302/304, dsPIC33FJ64MCX02/X04 AND dsPIC33FJ128MCX02/X04
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 4-2).
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 dsPIC33FJ32MC302/304, dsPIC33FJ64MCX02/
X04 and dsPIC33FJ128MCX02/X04 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.
dsPIC33FJ32MC302/304, dsPIC33FJ64MCX02/X04
and dsPIC33FJ128MCX02/X04 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 discussion of the interrupt vector
tables is provided in Section 7.1 “Interrupt Vector
Table”.
FIGURE 4-2:
PROGRAM MEMORY ORGANIZATION
msw
Address
0x000001
0x000003
0x000005
0x000007
most significant word
23
16
00000000
00000000
00000000
00000000
least significant word
8
Program Memory
‘Phantom’ Byte
(read as ‘0’)
Instruction Width
PC Address
(lsw Address)
0
0x000000
0x000002
0x000004
0x000006
DS70291E-page 40
© 2011 Microchip Technology Inc.