Datasheet

PIC24FJ128GC010 FAMILY
DS30009312B-page 74  2012-2013 Microchip Technology Inc.
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 mem-
ory not directly accessible by the lower 32-Kbyte data
address space and any external memory through the
Enhanced Parallel Master Port (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 4-4 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 register (DSRPAG) or Data Space Write 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).
The data addressing range of PIC24FJ128GC010 family
devices depends on the version of the Enhanced
Parallel Master Port (EPMP) implemented on a particu-
lar device; this is, in turn, is a function of the device pin
count. Table 4-40 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
“PIC24F Family Reference Manual”, Section 42.
“Enhanced Parallel Master Port (EPMP)” (DS39730).
.
FIGURE 4-4: EXTENDED DATA SPACE
TABLE 4-40: TOTAL ACCESSIBLE DATA
MEMORY
Family
Internal
RAM
External RAM
Access Using
EPMP
PIC24FJXXXGC010 8K Up to 16 Mbytes
PIC24FJXXXGC006 8K Up to 64K
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).
0000h
Special
Registers
32-Kbyte
EDS
8000h
Program Memory
DSxPAG
= 001h
DSx PAG
= 1FFh
DSRPAG
= 200h
DSRPAG
= 3FFh
Function
008000h
00FFFEh
000000h 7F8001h
FFFFFEh 007FFEh 7FFFFFh
Program
Space
0800h
FFFEh
EDS Pages
EPMP Memory Space
(1)
External
Memory
Access
Using
EPMP
(1)
FF8000h
DSRPAG
= 2FFh
7F8000h
7FFFFEh
Access
Program
Space
Access
Program
Space
Access
DSRPAG
= 300h
000001h
007FFFh
Program
Space
Access
Note 1: The range of addressable memory available is dependent on the device pin count and EPMP implementation.
External
Memory
Access
Using
EPMP
(1)
Internal
Data
Memory
Space
(up to
30 Kbytes)
(Lower
Word)
(Lower
Word)
(Upper
Word)
(Upper
Word)
Window