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: September 2023