PIC24FJ64GA310 datasheet(65/406 Pages) MICROCHIP

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DS39996F-page 65

PIC24FJ128GA310 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 mem-

ory 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 4-4 displays the entire EDS space. The EDS is

organized as pages, called EDS pages, with one page

equal to size of the EDS window (32 Kbytes). A partic-

ular 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 PIC24FJ128GA310 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 4-35

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 Refer-

ence Manual

”, Section 42. “Enhanced Parallel Master

Port (EPMP)”

(DS39730).

FIGURE 4-4:

EXTENDED DATA SPACE

TABLE 4-35:

TOTAL ACCESSIBLE DATA

MEMORY

Family

Internal

RAM

External RAM

Access Using

EPMP

PIC24FJXXXGA310

Up to 16 MB

PIC24FJXXXGA308

Up to 64K

PIC24FJXXXGA306

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

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

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