PIC24FJ64GA705 Datasheet, PDF (54/412 Pages) –

PIC24FJ256GA705 FAMILY
4.2.5 EXTENDED DATA SPACE (EDS)
The Extended Data Space (EDS) allows PIC24F
devices to address a much larger range of data than
would otherwise be possible with a 16-bit address
range. EDS includes any additional internal data
memory not directly accessible by the lower 32-Kbyte
data address space and any external memory through
EPMP.
In addition, EDS also allows read access to the
program memory space. This feature is called Program
Space Visibility (PSV) and is discussed in detail in
Section 4.3.3 “Reading Data from Program Memory
Using EDS”.
Figure 4-3 displays the entire EDS space. The EDS is
organized as pages, called EDS pages, with one page
equal to the size of the EDS window (32 Kbytes). A par-
ticular EDS page is selected through the Data Space
Read Page register (DSRPAG) or the Data Space Write
Page register (DSWPAG). For PSV, only the DSRPAG
register is used. The combination of the DSRPAG
register value and the 16-bit wide data address forms a
24-bit Effective Address (EA).
FIGURE 4-3:
EXTENDED DATA SPACE
Special
Function
Registers
Internal
Data
Memory
Space
0000h
0800h
047FEh
04800h
The data addressing range of the PIC24FJ256GA705
family devices depends on the version of the Enhanced
Parallel Master Port implemented on a particular device;
this is, in turn, a function of device pin count. Table 4-12
lists the total memory accessible by each of the devices
in this family. For more details on accessing external
memory using EPMP, refer to the “dsPIC33/PIC24 Fam-
ily Reference Manual”, “Enhanced Parallel Master
Port (EPMP)” (DS39730).
.
TABLE 4-12: TOTAL ACCESSIBLE DATA
MEMORY
Family
Internal
RAM
External RAM
Access Using
EPMP
PIC24FJXXXGA70X
16K
1K
Note:
Accessing Page 0 in the EDS window will
generate an address error trap as Page 0
is the base data memory (data locations,
0800h to 7FFFh, in the lower Data Space).
Unimplemented
8000h _008000h
018000h
EDS Pages
FF8000h
000000h
7F8000h
000001h
7F8001h
32-Kbyte
EDS
Window
External
Memory
Access
Using
EPMP⁽¹⁾
External
Memory
Access
Using
EPMP⁽¹⁾
External
Memory
Access
Using
EPMP⁽¹⁾
Program
Space
Access
(Lower
Word)
Program
Space
Access
(Lower
Word)
Program
Space
Access
(Upper
Word)
Program
Space
Access
(Upper
Word)
FFFEh
008800h
DSxPAG
= 001h
01FFFEh
DSxPAG
= 002h
FFFFFEh
DSxPAG
= 1FFh
EPMP Memory Space⁽¹⁾
007FFEh
DSRPAG
= 200h
7FFFFEh
DSRPAG
= 2FFh
007FFFh
DSRPAG
= 300h
Program Memory
Note 1: The range of addressable memory available is dependent on the device pin count and EPMP implementation.
7FFFFFh
DSRPAG
= 3FFh
DS30010118B-page 54
 2016 Microchip Technology Inc.