The MA-51 8051 Assembler is a comprehensive and powerful macro assembler, which is capable of generating both relocatable and absolute object files. MA-51 includes a macro instruction processor and is fully compatible with ASM-51.

MA-51 is fully integrated into the RIDE Integrated Development Environment.

Assembly statements

• Directives: are used to determine the way the assembler processes assembly language instructions.

• Controls: are used to determine the way the assembler generates the object and listing files. Controls may be used either on the command line or in the source module(s).

• Instructions: specify the source code to assemble.

Comments
Comments are used to make a program more readable. They are introduced with a ‘;’ and ignored by the assembler.

Keywords
Keywords are symbols used by the assembler that must not be redefined.

Symbols
Symbols can be defined before assembly instructions, but not before directives such as $INCLUDE, etc. In the variables segments (data, bit, xdata, code), symbols can be assigned to any address. A symbol is equivalent to the numerical value of the address at which it is allocated.

Labels
A label is a symbol used to mark a particular place in an assembly program. It may refer to program code, to variable space in internal data memory, to variable space in external data memory, or to constant data stored in code space.

Operands
Operands are arguments of instructions or directives. They may be divided into 3 groups:

• Numerical, string and character operands

• Address pointer

• Register name

Main 'registers'
The register names in the 8051 and its derivatives are pre-defined and listed below :

• A: 8-bit accumulator

• R0-R7: 8-bit general purpose registers

• DPTR: 16-bit data pointer generally used to address data in external data memory or program memory

• DPL: 8-bit register containing the 8 lower bits of DPTR

• DPH: 8-bit register containing the 8 upper bits of DPTR

• PC: 16-bit program counter

• C: carry flag

• AB: represents the 16-bit A and B register pair

• AR0-AR7: absolute data address of R0-R7 in the current register bank (RR0-RR7 are also accepted, for compatibility with previous versions of the assembler).