## ASST6 Assembler

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    ST6 REGISTER SET

    The following is a list of the ST6 registers used by ASST6:

            a       -       8-bit accumulator
            x,y     -       8-bit index registers
            v,w     -       8-bit scratch registers

    ST6 INSTRUCTION SET

         The following list specifies the format for each addressing
    mode supported by ASST6:

            r               register (a,x,y,w,v) addressing

            #data           immediate data byte

            dir or *dir     8-bit zero page addressing
                            0 <= dir <= 255

            ext             12-bit extended addressing

            (x) or (y)      register indirect addressing

            label           pc-relative branch addressing

    The  terms  data, dir, offset, ext, and label may all be expres-
    sions.

         Note that not all addressing modes are valid with every in-
    struction, refer to the ST6 technical data for valid modes.
    The  following  tables  list all ST6 mnemonics recognized by the
    ASST6 assembler.

    Inherent Instructions

            nop                     ret
            reti                    stop
            wait

    Conditional Branch Instructions

            jrc     label           jrnc    label
            jrz     label           jrnz    label
            jrr     #,*dir,label
            jrs     #,*dir,label

    Bit Manipulation Instructions

            set     #,*dir          res     #,*dir

    Single Operand Instructions

            clr     a               clr     *dir
            com     a

            dec     r               dec     *dir
            dec     (x)             dec     (y)
            inc     r               inc     *dir
            inc     (x)             inc     (y)

            rlc     a               sla     a

    Double Operand Instructions

            add     a,(x)           add     a,(y)
            add     a,*dir          addi    a,#

            and     a,(x)           and     a,(y)
            and     a,*dir          andi    a,#

            cp      a,(x)           cp      a,(y)
            cp      a,*dir          cpi     a,#

            sub     a,(x)           sub     a,(y)
            sub     a,*dir          subi    a,#

    Call to Subroutine and Jump Instructions

            call    ext             jmp     ext

    Load and Store Instructions

            ld      a,x             ld      a,y
            ld      a,v             ld      a,w

            ld      x,a             ld      y,a
            ld      v,a             ld      w,a

            ld      a,*dir          ld      *dir,a

            ld      a,(x)           ld      a,(y)
            ld      (x),a           ld      (y),a

            ldi     a,#             ld      *dir,#

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Last Updated: March 2021