Datasheet

© 2006 Microchip Technology Inc. Preliminary DS70178C-page 33
dsPIC30F1010/202X
FIGURE 3-5: DATA SPACE WINDOW INTO PROGRAM SPACE OPERATION
3.2 Data Address Space
The core has two data spaces. The data spaces can be
considered either separate (for some DSP instruc-
tions), or as one unified linear address range (for MCU
instructions). The data spaces are accessed using two
Address Generation Units (AGUs) and separate data
paths.
3.2.1 DATA SPACE MEMORY MAP
The data space memory is split into two blocks, X and
Y data space. A key element of this architecture is that
Y space is a subset of X space, and is fully contained
within X space. In order to provide an apparent linear
addressing space, X and Y spaces have contiguous
addresses.
When executing any instruction other than one of the
MAC class of instructions, the X block consists of the
256 byte data address space (including all Y
addresses). When executing one of the MAC class of
instructions, the X block consists of the 256 bytes data
address space excluding the Y address block (for data
reads only). In other words, all other instructions regard
the entire data memory as one composite address
space. The MAC class instructions extract the Y
address space from data space and address it using
EAs sourced from W10 and W11. The remaining X data
space is addressed using W8 and W9. Both address
spaces are concurrently accessed only with the MAC
class instructions.
A data space memory map is shown in Figure 3-6.
23 15 0
PSVPAG
(1)
15
15
EA<15> = 0
EA<15> = 1
16
Data
Space
EA
Data Space Program Space
8
15
23
0x0000
0x8000
0xFFFF
0x00
0x100100
0x001FFE
Data Read
Upper half of Data
Space is mapped
into Program Space
Note: PSVPAG is an 8-bit register, containing bits <22:15> of the program space address
(i.e., it defines the page in program space to which the upper half of data space is being mapped).
0x001200
Address
Concatenation
BSET CORCON,#2 ; PSV bit set
MOV #0x00, W0 ; Set PSVPAG register
MOV W0, PSVPAG
MOV 0x9200, W0 ; Access program memory location
; using a data space access