## AS6804 Assembler

####

       Requires the .setdp directive to specify the ram area.

    6804 REGISTER SET

    The following is a list of the 6804 registers used by AS6804:

            x,y     -       index registers

    6804 INSTRUCTION SET

       The  following  tables  list all 6804 mnemonics recognized by
    the AS6804 assembler.  The designation [] refers to  a  required
    addressing  mode  argument.   The  following  list specifies the
    format for each addressing mode supported by AS6804:

            #data           immediate data
                            byte or word data

            ,x              register indirect addressing

            dir             direct addressing
                            (see .setdp directive)
                            0 <= dir <= 255

            ext             extended addressing

            label           branch label

    The  terms data, dir, and ext may be expressions.  The label for
    the short branchs beq, bne, bcc, and bcs must not be external.

       Note  that  not all addressing modes are valid with every in-
    struction, refer to the 6804 technical data for valid modes.

    Inherent Instructions

            coma            decx
            decy            incx
            incy            rola
            rti             rts
            stop            tax
            tay             txa
            tya             wait

    Branch Instructions

            bne     label           beq     label
            bcc     label           bcs     label

    Single Operand Instructions

            add     []
            and     []
            cmp     []
            dec     []
            inc     []
            lda     []
            sta     []
            sub     []

    Jump and Jump to Subroutine Instructions

            jsr     []
            jmp     []

    Bit Test Instructions

            brclr   #data,[],label
            brset   #data,[],label

            bclr    #label,[]
            bset    #label,[]

    Load Immediate data Instruction

            mvi     [],#data

    6804 Derived Instructions

            asla
            bam     label
            bap     label
            bxmi    label
            bxpl    label
            bymi    label
            bypl    label
            clra
            clrx
            clry
            deca
            decx
            decy
            inca
            incx
            incy
            ldxi    #data
            ldyi    #data
            nop
            tax
            tay
            txa
            tya

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###### Last Updated: March 2025