PIC18F2221 MICROCHIP [Microchip Technology], PIC18F2221 Datasheet - Page 79

• Manufacturer Part Number: PIC18F2221
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

6.3
The TBLRD instruction is used to retrieve data from
program memory and place it into data RAM. Table
reads from program memory are performed one byte at
a time.
FIGURE 6-4:
EXAMPLE 6-1:
© 2007 Microchip Technology Inc.
READ_WORD
Instruction Register
Reading the Flash Program
Memory
(IR)
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
TBLRD*+
MOVF
MOVWF
TBLRD*+
MOVF
MOVWF
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
Program Memory
Preliminary
; 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.
PIC18F4321 FAMILY
TBLPTR = xxxxx1
TBLRD
Read Register
TABLAT
TBLPTR = xxxxx0
DS39689E-page 77