DSPIC30F6012 MICROCHIP [Microchip Technology], DSPIC30F6012 Datasheet - Page 36

• Manufacturer Part Number: DSPIC30F6012
• Description: High-Performance, 16-Bit Digital Signal Controllers
• Manufacturer: MICROCHIP [Microchip Technology]

dsPIC30F6011/6012/6013/6014
FIGURE 3-9:
TABLE 3-2:
All effective addresses are 16 bits wide and point to
bytes within the data space. Therefore, the data space
address range is 64 Kbytes or 32K words.
3.2.3
The core data width is 16 bits. All internal registers are
organized as 16-bit wide words. Data space memory is
organized in byte addressable, 16-bit wide blocks.
DS70117F-page 34
EA = an unimplemented address
W8 or W9 used to access Y data
space in a MAC instruction
W10 or W11 used to access X
data space in a MAC instruction
Attempted Operation
Non-MAC Class Ops (Read)
Indirect EA from any W
DATA SPACE WIDTH
SFR SPACE
(Y SPACE)
EFFECT OF INVALID
MEMORY ACCESSES
DATA SPACE FOR MCU AND DSP (MAC CLASS) INSTRUCTIONS EXAMPLE
Data Returned
0x0000
0x0000
0x0000
Indirect EA from W8, W9
Y SPACE
UNUSED
UNUSED
3.2.4
To help maintain backward compatibility with PIC
MCU devices and improve data space memory usage
efficiency, the dsPIC30F instruction set supports both
word and byte operations. Data is aligned in data mem-
ory and registers as words, but all data space EAs
resolve to bytes. Data byte reads will read the complete
word which contains the byte, using the LSb of any EA
to determine which byte to select. The selected byte is
placed onto the LSB of the X data path (no byte
accesses are possible from the Y data path as the MAC
class of instruction can only fetch words). That is, data
memory and registers are organized as two parallel
byte wide entities with shared (word) address decode
but separate write lines. Data byte writes only write to
the corresponding side of the array or register which
matches the byte address.
As a consequence of this byte accessibility, all effective
address calculations (including those generated by the
DSP operations which are restricted to word sized
data) are internally scaled to step through word aligned
memory. For example, the core would recognize that
Post-Modified Register Indirect Addressing mode
[Ws++] will result in a value of Ws + 1 for byte
operations and Ws + 2 for word operations.
MAC Class Ops (Read)
DATA ALIGNMENT
Indirect EA from W10, W11
SFR SPACE
© 2006 Microchip Technology Inc.
UNUSED
®