as31 - An Intel 8031/8051 assembler
as31 [-h] [-l] [-s] [-v] [-Aarg] [-Ffmt] [-Ofile] infile.asm
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
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
-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
-Aarg This option specifies a format specific string which is passed
to the format generator. Both format "tdr" and the srecord
formats use this option.
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 location 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 offset, 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.
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
As31 includes the following assembler directives:
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
.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
.END This directive is ignored.
Adds the value of expr to the location counter. Used to reserve
a block of uninitialized data. Expr should be in bytes.
- 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.
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.
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,
d or D This forces a number to decimal. Unless 0X was used. ie.
o or O This causes the number to be interpreted as octal. ie.
- 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
- 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.
Below is a sample assembly program.
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
jb F0, climbup ; climbing which way?
climbdn: rr A ; down - shift right
jnb ACC.0, write ; back for more
climbup: rl A ; up - shift left
jnb ACC.7, write ; back for more
.end ; this directive ignored.
Ken Stauffer (University of Calgary) <firstname.lastname@example.org>
Martin Langer <email@example.com>