## AS6816 Assembler

####

    68HC16 REGISTER SET

    The following is a list of the 68HC16 registers used by AS6816:

            a,b     -       8-bit accumulators
            d       -       16-bit accumulator <a:b>
            e       -       16-bit accumulator
            x,y,z   -       index registers
            k       -       address extension register
            s       -       stack pointer
            ccr     -       condition code

    68HC16 INSTRUCTION SET

       The  following  tables  list all 68HC16 mnemonics recognized by
    the AS6816 assembler.  The designation [] refers to  a  required
    addressing  mode  argument.   The  following  list specifies the
    format for each addressing mode supported by AS6816:

            #data           immediate data
                            byte or word data

            #xo,#yo         local immediate data (mac / rmac)

            label           branch label

            r               register
                            ccr,a,b,d,e,x,y,z,s

            ,x              zero offset register indexed addressing
            ,x8
            ,x16

            offset,x        register indexed addressing
                                 0 <= offset <= 255   ---  8-bit
                            -32768 <= offset <= -1    --- 16-bit
                               256 <= offset <= 32767 --- 16-bit
                            (external definition of offset
                             uses 16-bit mode)

            offset,x8       unsigned 8-bit offset indexed addressing
            offset,x16      signed 16-bit offset indexed addressing

            e,x             accumulator offset indexed addressing

            ext             extended addressing

            bank            64K bank number (jmp / jsr)

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

       Note  that  not all addressing modes are valid with every in-
    struction, refer to the 6816 technical data for valid modes.

    Instruction Notes

       Several  instructions  have  argument  conditions that can be
    confusing to the uninitiated.  The AIS, AIX, AIY, AIZ, ADDD, and
    ADDE instructions have 8 and 16 bit immediate forms:

            AIS     ii              and
            AIS     jjkk

    Where  each  argument  is  sign extended to 20 bits.  This means
    that the 8 bit value is between -128 and  +127  and  the  16 bit
    value  is between -32768 and +32765.  The assembler checks for a
    constant argument with a value from -128 to +127 and  emits  the
    8 bit  opcode and signed 8 bit value.  This implies that that an
    argument  0xFC, often used to specify a value of -4 when dealing
    with  8 bit  arguments,  is not -4 but +252.  The assembler will
    emit the 16 bit opcode and the value 0x00FC, not  what  was  ex-
    pected.

    Inherent Instructions

            aba             abx             aby             abz
            ace             aced            ade             adx
            ady             adz             aex             aey
            aez             bgnd            cba             daa
            ediv            edivs           emul            emuls
            fdiv            fmuls           idiv            ldhi
            lpstop          mul             nop             psha
            pshb            pshmac          pula            pulb
            pulmac          rtr             rts             sba
            sde             sted            swi             sxt
            tab             tap             tba             tbek
            tbsk            tbxk            tbyk            tbzk
            tde             tdmsk           tdp             ted
            tedm            tekb            tem             tmer
            tmet            tmxed           tpa             tpd
            tskb            tsx             tsy             tsz
            txkb            txs             txy             txz
            tykb            tys             tyx             tyz
            tzkb            tzs             tzx             tzy
            wai             xgab            xgde            xgdx
            xgdy            xgdz            xgex            xgey
            xgez

    Push/Pull Multiple Register Instructions

            pshm    r,...           pulm    r,...

    Short Branch Instructions

            bcc     label           bcs     label
            beq     label           bge     label
            bgt     label           bhi     label
            bhis    label           bhs     label
            ble     label           blo     label
            blos    label           bls     label
            blt     label           bmi     label
            bne     label           bpl     label
            bra     label           brn     label
            bvc     label           bvs     label
            bsr     label

    Long Branch Instructions

            lbcc    label           lbcs    label
            lbeq    label           lbge    label
            lbgt    label           lbhi    label
            lbhis   label           lbhs    label
            lble    label           lblo    label
            lblos   label           lbls    label
            lblt    label           lbmi    label
            lbne    label           lbpl    label
            lbra    label           lbrn    label
            lbvc    label           lbvs    label
            lbsr    label

    Bit Manipulation Instructions

            bclr    [],#data
            bset    [],#data

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

    Single Operand Instructions

            asla                    aslb
            asld                    asle
            aslm
            asl     []              aslw    []

            asra                    asrb
            asrd                    asre
            asrm
            asr     []              asrw    []

            clra                    clrb
            clrd                    clre
                                    clrm
            clr     []              clrw    []

            coma                    comb
            comd                    come
            com     []              comw    []

            deca                    decb
            dec     []              decw    []

            inca                    incb
            inc     []              incw    []

            lsla                    lslb
            lsld                    lsle
            lslm
            lsl     []              lslw    []

            lsra                    lsrb
            lsrd                    lsre
            lsr     []              lsrw    []

            nega                    negb
            negd                    nege
            neg     []              negw    []

            rola                    rolb
            rold                    role
            rol     []              rolw    []

            rora                    rorb
            rord                    rore
            ror     []              rorw    []

            tsta                    tstb
            tsta                    tste
            tst     []              tstw    []

    Double Operand Instructions

            adca    []              adcb    []
            adcd    []              adce    []

            adda    []              addb    []
            addd    []              adde    []

            anda    []              andb    []
            andd    []              ande    []

            bita    []              bitb    []

            cmpa    []              cmpb    []
            cpd     []              cpe     []

            eora    []              eorb    []
            eord    []              eore    []

            ldaa    []              ldab    []
            ldd     []              lde     []

            oraa    []              orab    []
            ord     []              ore     []

            sbca    []              sbcb    []
            sbcd    []              sbce    []

            staa    []              stab    []
            std     []              ste     []

            suba    []              subb    []
            subd    []              sube    []

    Index/Stack Register Instructions

            cps     []              cpx     []
            cpy     []              cpz     []

            lds     []              ldx     []
            ldy     []              ldz     []

            sts     []              stx     []
            sty     []              stz     []

    Jump and Jump to Subroutine Instructions

            jmp     bank,[]         jsr     bank,[]

    Condition Code Register Instructions

            andp    #data           orp     #data

    Multiply and Accumulate Instructions

            mac     #data           rmac    #data
            mac     #xo,#yo         rmac    #xo,#yo

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###### Last Updated: March 2025