PIC18F2420-I/SOC01 Microchip, PIC18F2420-I/SOC01 Datasheet - Page 79

• Manufacturer Part Number: PIC18F2420-I/SOC01
• Description: 28 pin, 16 kb flash, 3804 ram, 25 i/o...
• Manufacturer: Microchip

6.3
The TBLRD instruction is used to retrieve data from
program memory and places it into data RAM. Table
reads from program memory are performed one byte at
a time.
FIGURE 6-4:
EXAMPLE 6-1:
© 2008 Microchip Technology Inc.
READ_WORD
Reading the Flash Program
Memory
Instruction Register
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
TBLRD*+
MOVF
MOVWF
TBLRD*+
MOVFW
MOVF
(IR)
READS FROM FLASH PROGRAM MEMORY
READING A FLASH PROGRAM MEMORY WORD
CODE_ADDR_UPPER
TBLPTRU
CODE_ADDR_HIGH
TBLPTRH
CODE_ADDR_LOW
TBLPTRL
TABLAT, W
WORD_EVEN
TABLAT, W
WORD_ODD
(Even Byte Address)
FETCH
PIC18F2420/2520/4420/4520
Program Memory
; Load TBLPTR with the base
; address of the word
; read into TABLAT and increment
; get data
; read into TABLAT and increment
; get data
(Odd Byte Address)
TBLPTR points to a byte address in program space.
Executing TBLRD places the byte pointed to into
TABLAT. In addition, TBLPTR can be modified
automatically for the next table read operation.
The internal program memory is typically organized by
words. The Least Significant bit of the address selects
between the high and low bytes of the word. Figure 6-4
shows the interface between the internal program
memory and the TABLAT.
TBLPTR = xxxxx1
TBLRD
Read Register
TABLAT
TBLPTR = xxxxx0
DS39631E-page 77