## AS8051 Assembler

####

    ACKNOWLEDGMENT

       Thanks  to  John  Hartman  for his contribution of the AS8051
    cross assembler.

            John L. Hartman
            jhartman@compuserve.com

####

    8051 REGISTER SET

            The following is a list of the 8051 registers used by AS8051:

                    a,b             -       8-bit accumulators
                    r0,r1,r2,r3     -       8-bit registers
                    r4,r5,r6,r7
                    dptr            -       data pointer
                    sp              -       stack pointer
                    pc              -       program counter
                    psw             -       status word
                    c               -       carry (bit in status word)

    8051 INSTRUCTION SET

       The  following  tables  list all 8051 mnemonics recognized by
    the AS8051 assembler.  The following list specifies  the  format
    for each addressing mode supported by AS8051:

            #data           immediate data
                            byte or word data

            r,r1,r2         register r0,r1,r2,r3,r4,r5,r6, or r7

            @r              indirect on register r0 or r1
            @dptr           indirect on data pointer
            @a+dptr         indirect on accumulator
                            plus data pointer
            @a+pc           indirect on accumulator
                            plus program counter

            addr            direct memory address

            bitaddr         bit address

            label           call or jump label

    The terms data, addr, bitaddr, and label may all be expressions.

       Note  that  not all addressing modes are valid with every in-
    struction.  Refer to the 8051 technical data for valid modes.

    Inherent Instructions

            nop

    Move Instructions

            mov     a,#data         mov     a,addr
            mov     a,r             mov     a,@r

            mov     r,#data         mov     r,addr
            mov     r,a

            mov     addr,a          mov     addr,#data
            mov     addr,r          mov     addr,@r
            mov     addr1,addr2     mov     bitaddr,c

            mov     @r,#data        mov     @r,addr
            mov     @r,a

            mov     c,bitaddr
            mov     dptr,#data

            movc    a,@a+dptr       movc    a,@a+pc
            movx    a,@dptr         movx    a,@r
            movx    @dptr,a         movx    @r,a

    Single Operand Instructions

            clr     a               clr     c
            clr     bitaddr
            cpl     a               cpl     c
            cpl     bitaddr
            setb    c               setb    bitaddr

            da      a
            rr      a               rrc     a
            rl      a               rlc     a
            swap    a

            dec     a               dec     r
            dec     @r
            inc     a               inc     r
            inc     dptr            inc     @r

            div     ab              mul     ab

            pop     addr            push    addr

    Two Operand Instructions

            add     a,#data         add     a,addr
            add     a,r             add     a,@r
            addc    a,#data         addc    a,addr
            addc    a,r             addc    a,@r
            subb    a,#data         subb    a,addr
            subb    a,r             subb    a,@r
            orl     a,#data         orl     a,addr
            orl     a,r             orl     a,@r
            orl     addr,a          orl     addr,#data
            orl     c,bitaddr       orl     c,/bitaddr
            anl     a,#data         anl     a,addr
            anl     a,r             anl     a,@r
            anl     addr,a          anl     addr,#data
            anl     c,bitaddr       anl     c,/bitaddr
            xrl     a,#data         xrl     a,addr
            xrl     a,r             xrl     a,@r
            xrl     addr,a          xrl     addr,#data
            xrl     c,bitaddr       xrl     c,/bitaddr
            xch     a,addr          xch     a,r
            xch     a,@r            xchd    a,@r

    Call and Return Instructions

            acall   label           lcall   label
            ret                     reti
            in      data
            out     data
            rst     data

    Jump Instructions

            ajmp    label
            cjne    a,#data,label   cjne    a,addr,label
            cjne    r,#data,label   cjne    @r,#data,label
            djnz    r,label         djnz    addr,label
            jbc     bitadr,label
            jb      bitadr,label    jnb     bitadr,label
            jc      label           jnc     label
            jz      label           jnz     label
            jmp     @a+dptr
            ljmp    label           sjmp    label

    Predefined Symbols:  SFR Map

                    --------- 4 Bytes ----------
                    ----    ----    ----    ----
            FC                                          FF
            F8                                          FB
            F4                                          F7
            F0      B                                   F3
            EC                                          EF
            E8                                          EB
            E4                                          E7
            E0      ACC                                 E3
            DC                                          DF
            D8                                          DB
            D4                                          D7
            D0      PSW                                 D3
            CC   [  TL2     TH2                     ]   CF
            C8   [  T2CON           RCAP2L  RCAP2H  ]   CB
            C4                                          C7
            C0                                          C3
            BC                                          BF
            B8      IP                                  BB
            B4                                          B7
            B0      P3                                  B3
            AC                                          AF
            A8      IE                                  AB
            A4                                          A7
            A0      P2                                  A3
            9C                                          9F
            98      SCON    SBUF                        9B
            94                                          97
            90      P1                                  93
            8C      TH0     TH1                         8F
            88      TCON    TMOD    TL0     TL1         8B
            84                              PCON        87
            80      P0      SP      DPL     DPH         83

            [...] Indicates Resident in 8052, not 8051
            A is an allowed alternate for ACC.

    Predefined Symbols:  SFR Bit Addresses

                    ---------- 4 BITS ----------
                    ----    ----    ----    ----
            FC                                          FF
            F8                                          FB
            F4      B.4     B.5     B.6     B.7         F7
            F0      B.0     B.1     B.2     B.3         F3
            EC                                          EF
            E8                                          EB
            E4      ACC.4   ACC.5   ACC.6   ACC.7       E7
            E0      ACC.0   ACC.1   ACC.2   ACC.3       E3
            DC                                          DF
            D8                                          DB
            D4      PSW.4   PSW.5   PSW.6   PSW.7       D7
            D0      PSW.0   PSW.1   PSW.2   PSW.3       D3
            CC   [  T2CON.4 T2CON.5 T2CON.6 T2CON.7 ]   CF
            C8   [  T2CON.0 T2CON.1 T2CON.2 T2CON.3 ]   CB
            C4                                          C7
            C0                                          C3
            BC      IP.4    IP.5    IP.6    IP.7        BF
            B8      IP.0    IP.1    IP.2    IP.3        BB
            B4      P3.4    P3.5    P3.6    P3.7        B7
            B0      P3.0    P3.1    P3.2    P3.3        B3
            AC      IE.4    IE.5    EI.6    IE.7        AF
            A8      IE.0    IE.1    IE.2    IE.3        AB
            A4      P2.4    P2.5    P2.6    P2.7        A7
            A0      P2.0    P2.1    P2.2    P2.3        A3
            9C      SCON.4  SCON.5  SCON.6  SCON.7      9F
            98      SCON.0  SCON.1  SCON.2  SCON.3      9B
            94      P1.4    P1.5    P1.6    P1.7        97
            90      P1.0    P1.1    P1.2    P1.3        93
            8C      TCON.4  TCON.5  TCON.6  TCON.7      8F
            88      TCON.0  TCON.1  TCON.2  TCON.3      8B
            84      P0.4    P0.5    P0.6    P0.7        87
            80      P0.0    P0.1    P0.2    P0.3        83

            [...] Indicates Resident in 8052, not 8051
            A is an allowed alternate for ACC.

    Predefined Symbols:  Control Bits

                    ---------- 4 BITS ----------
                    ----    ----    ----    ----
            FC                                          FF
            F8                                          FB
            F4                                          F7
            F0                                          F3
            EC                                          EF
            E8                                          EB
            E4                                          E7
            E0                                          E3
            DC                                          DF
            D8                                          DB
            D4      RS1     F0      AC      CY          D7
            D0      P               OV      RS0         D3
            CC   [  TLCK    RCLK    EXF2    TF2     ]   CF
            C8   [  CPRL2   CT2     TR2     EXEN2   ]   CB
            C4                                          C7
            C0                                          C3
            BC      PS      PT2                         BF
            B8      PX0     PT0     PX1     PT1         BB
            B4                                          B7
            B0      RXD     TXD     INT0    INT1        B3
            AC      ES      ET2             EA          AF
            A8      EX0     ET0     EX1     ET1         AB
            A4                                          A7
            A0                                          A3
            9C      REN     SM2     SM1     SM0         9F
            98      RI      TI      RB8     TB8         9B
            94                                          97
            90                                          93
            8C      TR0     TF0     TR1     TF1         8F
            88      IT0     IE0     IT1     IE1         8B
            84                                          87
            80                                          83

            [...] Indicates Resident in 8052, not 8051

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###### Last Updated: March 2025