Entering an ASM instruction via SBCMON is only really sensible for a quick hack.

Normally you would write your ASM program in a text editor. Assemble it and download the HEX file to your 8051. This way you can use the full power of your text editor to move blocks of code around, use symbols for your variables and have complicated expressions as arguments.

Your source file is safely on disk, and any bugs or mishaps on your 8051 board can be restored by just reloading the HEX file.

As you go debugging your masterpiece, you edit the source code, re-assemble, re-load the HEX file.

Occasionally you may just want to try changing one branch value or register content. SBCMON will let you do this but only with a very simple syntax. And most importantly any quick hack like this is not in your disk source code. So it is a recipe for disaster.

Providing you are aware of this, it is obviously quite handy to test the odd simple instruction. To insert extra instructions requires you checking all spanning branches are corrected. This is generally far more trouble than it is worth.

David.