Microchip Technology dsPIC30F - Section 5. Flash and Eeprom Programming

© 2004 Microchip Technology Inc. DS70052C-page 5-3
Section 5. Flash and EEPROM Programming
Flash and EEPROM
Programming
5
Figure 5-1: Addressing for Table Instructions
5.2.1 Using Table Read Instructions
Table reads require two steps. First, an address pointer is setup using the TBLPAG register and
one of the W registers. Then, the program memory contents at the address location may be read.
5.2.1.1 Read Word Mode
The following code example shows how to read a word of program memory using the table
instructions in Word mode:
; Setup the address pointer to program space
MOV #tblpage(PROG_ADDR),W0 ; get table page value
MOV W0,TBLPAG ; load TBLPAG register
MOV #tbloffset(PROG_ADDR),W0 ; load address LS word
; Read the program memory location
TBLRDH [W0],W3 ; Read high byte to W3
TBLRDL [W0],W4 ; Read low word to W4
5.2.1.2 Read Byte Mode
; Setup the address pointer to program space
MOV #tblpage(PROG_ADDR),W0 ; get table page value
MOV W0,TBLPAG ; load TBLPAG register
MOV #tbloffset(PROG_ADDR),W0 ; load address LS word
; Read the program memory location
TBLRDH.B [W0],W3 ; Read high byte to W3
TBLRDL.B [W0++],W4 ; Read low byte to W4
TBLRDL.B [W0++],W5 ; Read middle byte to W5
In the code example above, the post-increment operator on the read of the low byte causes the
address in the working register to increment by one. This sets EA<0> to a ‘1’ for access to the
middle byte in the third write instruction. The last post-increment sets W0 back to an even
address, pointing to the next program memory location.
TBLPAG
8 bits from TBLPAG
EA
EA<0> Selects Byte
24-bit EA
TBLPAG<7> Selects
User/Configuration
Space
0
15
0
7
16 bits from Wn
Note: The tblpage() and tbloffset() directives are provided by the Microchip
assembler for the dsPIC30F. These directives select the appropriate TBLPAG and
W register values for the table instruction from a program memory address value.
Refer to the Microchip software tools documentation for further details.