WF AUTOMA_AO <PICLIST@MITVMA.MIT.EDU> wrote:

> Did someone have experience how to write and read a information at
> 8000H external position memory! Using the PIC17c42 assembly code?

mIGUEL:

To read the contents of address 8000H into registers HIBYTE and
LOBYTE:

    MOVLW   HIGH (08000H)   ;TBLPTR points to 08000H.
    MOVWF   TBLPTRH         ;
    MOVLW   LOW (08000H)    ;
    MOVWF   TBLPTRL         ;

    TABLRD  0,0,LOBYTE          ;Copy the 16-bit data from 08000H into the
                            ;table latch.

    TLRD    0,LOBYTE        ;Copy the low 8 bits from the table latch
                            ;into the "LOBYTE" register.

    TLRD    1,HIBYTE        ;Copy the high 8 bits from the table
                            ;latch into the "HIBYTE" register.

To write the contents of registers HIBYTE and LOBYTE to address
8000H:

    MOVLW   HIGH (08000H)   ;TBLPTR points to 08000H.
    MOVWF   TBLPTRH         ;
    MOVLW   LOW (08000H)    ;
    MOVWF   TBLPTRL         ;

    TLWT    0,LOBYTE        ;Copy the contents of the "LOBYTE"
                            ;register to the low 8 bits of the
                            ;table latch.

    TABLWT  1,0,HIBYTE      ;Copy the contents of the "HIBYTE"
                            ;register to the high 8 bits of the
                            ;table latch, then copy the contents
                            ;of the table latch to address 8000H.

You may want to look at Microchip's appnote AN548; it's probably on
the Microchip web site.

-Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499