PIC24FJ256DA206 datasheet(73/408 Pages) MICROCHIP

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DS39969B-page 73

PIC24FJ256DA210 FAMILY

4.2.5.2

Data Write into EDS Space

In order to write data to EDS space, such as in EDS

reads, an Address Pointer is set up by loading the

required EDS page number into the DSWPAG register,

and assigning the offset address to one of the W regis-

ters. Once the above assignment is done, then the

EDS window is enabled by setting bit 15 of the working

accessed location can be written.

Figure 4-2 illustrates how the EDS space address is

generated for write operations.

FIGURE 4-6:

EDS ADDRESS GENERATION FOR WRITE OPERATIONS

When the MSBs of EA is ‘1’, the lower 9 bits of

DSWPAG are concatenated to the lower 15 bits of EA

to form a 24-bit EDS address for write operations.

Example 4-2 shows how to write a byte, word and dou-

ble-word to EDS.

EXAMPLE 4-2:

EDS WRITE CODE IN ASSEMBLY

DSWPAG Reg

Select

15 Bits

9 Bits

24-Bit EA

Wn<0> is Byte Select

; Set the EDS page where the data to be written

mov

#0x0002 , w0

mov

w0 , DSWPAG

;page 2 is selected for write

mov

#0x0800 ,

;select the location (0x800) to be written

bset

w1 , #15

;set the MSB of the base address, enable EDS mode

;Write a byte to the selected location

mov

#0x00A5 , w2

mov

#0x003C , w3

mov.b

w2 , [w1++]

;write Low byte

mov.b

w3 , [w1++]

;write High byte

;Write a word to the selected location

mov

#0x1234

, w2

;

mov

w2 , [w1]

;

;Write a Double - word to the selected location

mov

#0x1122 , w2

mov

#0x4455 , w3

mov.d

w2 , [w1]

;2 EDS writes

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