Assembler: please kick me in the right direction

[Darrel Taylor]

This page describes the 8051 registers, but the whole site is pretty good too.
http://www.8052.com/tutbregs.phtml#R%20Registers

The MUL?xxx macro usually has 3 paramaters, the third one is the result of multiplying the first two.

For instance, if you had the following variables ...

A  VAR  BYTE
B  VAR  BYTE
Y  VAR  BYTE
Z  VAR  WORD

THEN ...

  this ASM macro              is same as this PBP statement
  ---------------------       -------------------------
    MUL?BBB   _A, _B, _Y          Y = A * B
    MUL?BBW   _A, _B, _Z          Z = A * B
    MUL?BWW   _A, _Z, _Z          Z = A * Z

And, you can see that often it's easier to just jump out of ASM and handle it in Basic.

------------------
If you do use the MUL? macros, there's something else you have to do to get them to work. Since, they are from the PBPPIC14.MAC file, they don't automaticaly get included with the project. So you have to Trick PBP into thinking it needs those macros.

This bit of code doesn't use any Program space since the ifdef keeps it from being compiled. But PBP sees the statements and includes any macros that are associated with them.

@  ifdef DoNotCompile                        ' Macro to include
       R0.LowByte = R0.LowByte * R0.LowByte  ' MUL?BBB
       R0 = R0.LowByte * R0.LowByte          ' MUL?BBW
       R0 = R0.LowByte * R0                  ' MUL?BWW
@  endif

But then, If you do it in Basic, you don't have to worry about it.

Merry X-Mas,
Darrel