There are several things to consider if you decide to wisely spend money on engineering and marketing...

1) Use the protect mode features offered by the MCU that you intend to use.

2) Include some simple things in your code that make it harder to simply blot out things like a copyright string. One example is to place a CRC-32 value into the image of the FLASH and have that be checked at bootup across the whole flash space image.

3) Make your products so that the MCU cannot be used without the hardware and the MCU firmware cannot be used without the hardware. 8051's cannot do one thing that is effective for this recommendation. For MCUs that can execute code out of internal RAM you load a key element subroutine out of a serial FLASH or EEPROM into the Intenal RAM and execute it there.

4) Write the code in C language.

There are a multitude of other things one can do to make it harder to clone product code but as the complexity rises you need to evaluate the engineering cost to implement it versus the incremental benefit that it brings.

Michael Karas