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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: April 2009