assembler for 8051 microcontroller, i wrote this in 1990. It has been used a lot in the public domain (e.g., www.pjrc.com )
Manual
AS31(1) General Commands Manual AS31(1)
NAME
as31 - An Intel 8031/8051 assembler
SYNOPSIS
as31 [-h] [-l] [-s] [-v] [-Aarg] [-Ffmt] [-Ofile] infile.asm
DESCRIPTION
As31 assembles infile.asm into one of several different output formats. The output will be
in a file called infile.obj. The .asm extenstion is required.
OPTIONS
The options must appear before the input file name. Both options are optional. The text of
each flag must appear on the same argument as the flag. For example, "-Fod" is a valid
argument, but "-F od" is not.
-h This causes the assembler to print out a verbose message describing its options.
The message is written to the standard error.
-l This option tells the assembler to also generate a listing file. A listing will be
placed in the file infile.lst. Where 'infile' is the file that is being assembled.
This option may appear anywhere before infile.asm. The option must occur isolated
on the command line.
The listing file shows the assembler generated code in hex, and up to 60 characters
are retained from the source file.
-s This causes the assembler to write output to standard output.
-v This causes the assembler to print a version number to the standard output.
-Aarg This option specifies a format specific string which is passed to the format gener‐
ator. Both format "tdr" and the srecord formats use this option.
-Fformat
This options specifies the output format that is to be used.
Currently the only options available for this are:
hex This format is the Intel HEX format which is expected by a number of EPROM
programmers and the PAULMON debugger. For use with some programmers, the
output file's extension may have to be changed to .HEX to be recognized by
the programmer. No -A option is used. This format should be the default if
no -F option is used.
tdr This format generates an asci file of hex digits formatted in such a way, so
that they can be read by tdr's debugger. An argument can be specified (See
-A option) which will pass a format specific string to the format generator.
In this case, the argument string represents an offset to add to the loca‐
tion counter. This offset is specified in decimal and defaults to 64*1024
(0x10000). To specify and offset of 100, you would need "-Ftdr -A100" when
invoking the assembler.
byte This format is simply an address and a byte on each line, in ascii. No -A
option is used.
od This format is similar to the output from od(1). The format consists of an
address followed by sixteen hexadecimal bytes, followed by the equivilant
ASCII. No -A option is used.
srec2, srec3, srec4
The srecord generator is capable of generating output with any one of 2, 3,
or 4 byte addresses. The -A option can be used to set the base address off‐
set, the default here is 0x0000 (unlike tdr).
NOTE: This assembler allows for the output formats to be expanded to include many
different output formats.
-Ofile This option tells the assembler to write the output to a file.
ASSEMBLER INSTRUCTIONS
This assembler accepts standard 8031/8051 instruction formats. Below is a list of
instructions and addressing modes.
INSTRUCTION BYTES CYCLES
----------- ----- ------
ACALL addr11 2 24
ADD A, #data8 2 12
ADD A, @Ri 1 12
ADD A, Rn 1 12
ADD A, direct 2 12
ADDC A, #data8 2 12
ADDC A, @Ri 1 12
ADDC A, Rn 1 12
ADDC A, direct 2 12
AJMP addr11 2 24
ANL A, #data8 2 12
ANL A, @Ri 1 12
ANL A, Rn 1 12
ANL A, direct 2 12
ANL C, /bit 2 24
ANL C, !bit 2 24
ANL C, bit 2 24
ANL direct, #data8 3 24
ANL direct, A 2 12
CJNE @Ri, #data8, rel 3 24
CJNE A, #data8, rel 3 24
CJNE A, direct, rel 3 24
CJNE Rn, #data8, rel 3 24
CLR A 1 12
CLR C 1 12
CLR bit 2 12
CPL A 1 12
CPL C 1 12
CPL bit 2 12
DA A 1 12
DEC @Ri 1 12
DEC A 1 12
DEC DPTR 1 12
DEC Rn 1 12
DEC direct 2 12
DIV AB 1 48
DJNZ Rn, rel 2 24
DJNZ direct, rel 3 24
INC @Ri 1 12
INC A 1 12
INC DPTR 1 24
INC Rn 1 12
INC direct 2 12
JB bit, rel 3 24
JBC bit, rel 3 24
JC relative 2 24
JMP @A + DPTR 1 24
JMP @DPTR + A 1 24
JNB bit, rel 3 24
JNC relative 2 24
JNZ relative 2 24
JZ relative 2 24
LCALL addr16 3 24
LJMP addr16 3 24
MOV @Ri, #data8 2 12
MOV @Ri, A 1 12
MOV @Ri, direct 2 24
MOV A, #data8 2 12
MOV A, @Ri 1 12
MOV A, Rn 1 12
MOV A, direct 2 12
MOV C, bit 2 12
MOV DPTR, #data16 3 24
MOV Rn, #data8 2 12
MOV Rn, A 1 12
MOV Rn, direct 2 24
MOV bit, C 2 24
MOV direct, #data8 3 24
MOV direct, @Ri 2 24
MOV direct, A 2 12
MOV direct, Rn 2 24
MOV direct, direct 3 24
MOVC A, @A + DPTR 1 24
MOVC A, @A + PC 1 24
MOVC A, @DPTR + A 1 24
MOVC A, @PC + A 1 24
MOVX @DPTR, A 1 12
MOVX @Ri, A 1 24
MOVX A, @DPTR 1 24
MOVX A, @Ri 1 24
MUL AB 1 48
NOP 1 12
ORL A, #data8 2 12
ORL A, @Ri 1 12
ORL A, Rn 1 12
ORL A, direct 2 12
ORL C, /bit 2 24
ORL C, !bit 2 24
ORL C, bit 2 24
ORL direct, #data8 3 24
ORL direct, A 2 12
POP direct 2 24
PUSH direct 2 24
RET 1 24
RETI 1 24
RL A 1 12
RLC A 1 12
RR A 1 12
RRC A 1 12
SETB A 1 12
SETB bit 2 12
SJMP relative 2 24
SUBB A, #data8 2 12
SUBB A, @Ri 1 12
SUBB A, Rn 1 12
SUBB A, direct 2 12
SWAP A 1 12
XCH A, #data8 2 12
XCH A, @Ri 1 12
XCH A, Rn 1 12
XCH A, direct 2 12
XCHD A, #data8 2 12
XCHD A, @Ri 1 12
XCHD A, Rn 1 12
XCHD A, direct 2 12
XRL A, #data8 2 12
XRL A, @Ri 1 12
XRL A, Rn 1 12
XRL A, direct 2 12
XRL direct, #data8 3 12
XRL direct, A 2 12
ASSEMBLER DIRECTIVES
As31 includes the following assembler directives:
.ORG expr
Start assembling at the address specified by the expression expr. An error occurs
if the assembler starts assembling over an address space that has previously been
assembled into.
.EQU symbol, expr
Set symbol to the value of expr. The value for expr must be known during the first
pass, when the line containing the .EQU is encountered.
.BYTE expr, expr, ...
Assemble the bytes specified by the expression into memory. A string may also be
specified with this directive.
.WORD expr, expr, ...
Assemble the words specified by the expression into memory. The byte ordering
used, is that used by the 8031.
.FLAG symbol1, symbol.[0-7]
Sets symbol1 to the bit address specified by the symbol.[0-7] expression. Where
[0-7] denotes a character between 0 and 7. The resulting bit address is checked to
see if it is a valid bit address.
.END This directive is ignored.
.SKIP expr
Adds the value of expr to the location counter. Used to reserve a block of unini‐
tialized data. Expr should be in bytes.
LEXICAL CONVENTIONS
- All characters following a semi-colon are ignored until a newline is encountered.
- All numbers default to decimal, unless the number starts with one of the following:
0x or 0X
This indicates a hexadecimal number. ie. 0x00ff
0b or 0B
This indicates a binary number. (1's and 0's). ie. 0b1100110010
0 This indicates an octal number. ie. 0377
- All numbers default to decimal, unless the number ends with one of the following
characters:
b or B This indicates a binary number. Unless 0x was used above. ie. 1010101b
h or H This always indicates a hex number, However the if the first character is
non-numerical, then either 0x or 0 must be specified. This avoids confusing
the assembler into thinking a hex number is a symbol. For example: 0ffh,
0xffh, 0XffH, 20h, 0x20 and 020h are means to specify a valid hexdigit. But
the following are not: ffh, 0ff.
d or D This forces a number to decimal. Unless 0X was used. ie. 129d
o or O This causes the number to be interpreted as octal. ie. 377o
- A character constant can be entered as 'c' where c is some character. \b, \n, \r,
\t, \' \0 are also valid. A character constant can be used anywhere that an integer
value can.
- A string is entered as a set of characters enclosed in double quotes "". A string
is only valid with the .BYTE directive. \b, \n, \r, \t, \" are also valid escapes.
However \0 is not.
- Instructions, directives, and the symbols: R0, R1, R2, R3, R4, R5, R6, R7, A, AB,
and C can be entered in upper or lower case without assembler confusion. These
words however cannot be defined as a user symbol. Any user symbol may be used, and
case will be preserved. So the user symbols "foo" and "Foo" are different, but
"addc" is the same as "aDdC".
- A symbol can be any alpha numerical character plus the underscore ('_').
- Expressions are accepted in most places where a value or a symbol is needed. An
expression consists of the following operators. All operators evaulate to integer
objects (higher precedence opertors listed first):
- Unary minus
& Bit-wise AND.
| Bit-Wise OR.
* Integer multiplication.
/ Integer division
% Integer modulus
+ Integer addition.
- Integer subtraction.
- In addition to these operators, a special symbol '*' may be used to represent the
current location counter.
EXAMPLES
Below is a sample assembly program.
.org 0
start: mov P3, #0xff ; use alternate fns on P3
; leds on P1 are inverted.
setb F0 ; climbing up
mov A, #0x01 ; initial bit
write: cpl A ; write it
mov P1, A
cpl A
acall delay
jb F0, climbup ; climbing which way?
climbdn: rr A ; down - shift right
jnb ACC.0, write ; back for more
setb F0
ajmp write
climbup: rl A ; up - shift left
jnb ACC.7, write ; back for more
clr F0
ajmp write
.end ; this directive ignored.
AUTHORS
Ken Stauffer (University of Calgary) <@cpsc.ucalgary.ca>