PIC24FJ64GA306-I/MR Microchip Technology, PIC24FJ64GA306-I/MR Datasheet - Page 66

• Manufacturer Part Number: PIC24FJ64GA306-I/MR
• Description: 16-bit, 16 MIPS, 64 KB Flash, 8 KB RAM, 53 I/O, LCD, XLP W/Vbat 64 QFN 9x9x0.9mm
• Manufacturer: Microchip Technology

PIC24FJ128GA310 FAMILY
4.2.5.1
In order to read the data from the EDS space, first, an
Address Pointer is set up by loading the required EDS
page number into the DSRPAG register and assigning
the offset address to one of the W registers. Once the
above assignment is done, the EDS window is enabled
by setting bit 15 of the working register, assigned with
the offset address; then, the contents of the pointed
EDS location can be read.
Figure 4-5
generated for read operations.
When the Most Significant bit (MSBs) of EA is ‘1’ and
DSRPAG<9> = 0, the lower 9 bits of DSRPAG are con-
catenated to the lower 15 bits of EA to form a 24-bit
EDS space address for read operations.
FIGURE 4-5:
EXAMPLE 4-1:
DS39996F-page 66
; Set the EDS page from where the data to be read
;Read a byte from the selected location
;Read a word from the selected location
;Read Double - word from the selected location
mov
mov
mov
bset
mov.b
mov.b
mov
mov.d
illustrates how the EDS space address is
Data Read from EDS
#0x0002 , w0
w0 , DSRPAG
#0x0800 ,
w1 , #15
[w1++] ,
[w1++] , w3
[w1] , w2
[w1] , w2
9
EDS ADDRESS GENERATION FOR READ OPERATIONS
EDS READ CODE IN ASSEMBLY
0 = Extended SRAM and EPMP
8
DSRPAG Reg
9 Bits
w1
w2
Select
;page 2 is selected for read
;select the location (0x800) to be read
;set the MSB of the base address, enable EDS mode
;read Low byte
;read High byte
;
;two word read, stored in w2 and w3
0
1
24-Bit EA
Example 4-1
double-word from EDS.
Note:
Wn
15 Bits
All read operations from EDS space have
an overhead of one instruction cycle.
Therefore, a minimum of two instruction
cycles is required to complete an EDS
read. EDS reads under the REPEAT
instruction; the first two accesses take
three
accesses take one cycle.
shows how to read a byte, word and
Wn<0> is Byte Select
 2010-2011 Microchip Technology Inc.
cycles
and
the
subsequent