## AS740 Assembler

####

    ACKNOWLEDGMENT

         Thanks  to  Uwe  Steller  for his contribution of the AS740
    cross assembler.

            Uwe Stellar
            Uwe dot Steller at t-online dot de

         The  instruction  syntax  of  this cross assembler uses the
    square brackets [] to denote addressing indirection.

####

    740 REGISTER SET

    The following is a list of the 740 registers used by AS740:

            a       -       8-bit accumulator
            x,y     -       index registers

    740 INSTRUCTION ADDRESSING MODES

    The following list specifies the format for each
    addressing mode supported by AS740:

            #data           immediate data byte

            #data,*zp       immediate data to zero page

            a               accumulator addressing

            *zp             zero page addressing
                            (see .setdp directive)
                            0 <= dir <= 255

            *zp,x           zero page x addressing
            *zp,y           zero page y addressing
                            address = (offset + (x or y))

            [*zp,x]         indirect x addressing
                            0 <= offset <= 255
                            address = 2 bytes at location
                                [(offset + (x or y)) mod 256]

            [*zp],y         indirect y addressing
                            address = 2 byte value at offset
                                plus the value of the y register

            abs             absolute addressing (2 byte)
            abs,x           absolute x addressing (2 byte + x)
            abs,y           absolute y addressing (2 byte + y)

            [abs]           indirect addressing (2 byte)

            label           branch label

            \special        low order byte of address 0xFFnn

            BIT#,*zp        bit set/clear zero page
            BIT#,A          bit set/clear accumulator

            BIT#,*zp,label  branch on bit set/clear in zero page
            BIT#,A,label    branch on bit set/clear in accumulator

    The terms data, zp, abs, BIT , special, and label may all be ex-
    pressions.

         Note that not all addressing modes are valid with every in-
    struction, refer to the 740 technical data for valid modes.

####

    740 INSTRUCTION SET

         The  following  tables list all 740 family mnemonics recog-
    nized by the AS740 assembler.  The designation []  refers  to  a
    required addressing mode argument.

    Inherent Instructions

            brk                     clc
            cld                     cli
            clt                     clv
            dex                     dey
            inx                     iny
            nop                     pha
            php                     pla
            plp                     rti
            rts                     sec
            sed                     sei
            set                     stp
            tax                     tay
            tsx                     txa
            txs                     tya
            wit

    Branch Instructions

            bcc     label           bhs     label
            bcs     label           blo     label
            beq     label           bmi     label
            bne     label           bpl     label
            bvc     label           bvs     label
            bra     label

    Single Operand Instructions

            asl     []
            dec     []
            inc     []
            lsr     []
            rol     []
            ror     []

    Double Operand Instructions

            adc     []
            and     []
            bit     []
            cmp     []
            eor     []
            lda     []
            ora     []
            sbc     []
            sta     []

    Jump and Jump to Subroutine Instructions

            jmp     []              jsr     []

    Miscellaneous X and Y Register Instructions

            cpx     []
            cpy     []
            ldx     []
            stx     []
            ldy     []
            sty     []

    Bit Instructions

            bit     []
            bbc     BIT#,[],label           bbs     BIT#,[],label
            clb     BIT#,[]                 seb     BIT#,[]

    Other Instructions

            div     []                      mul     []
            ldm     #imm,[]                 com     []
            tst     []                      rrf     []

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###### Last Updated: March 2025