C51: Unused Opcodes

Information in this article applies to:

• C51 All Versions

QUESTION

I'm currently developing a device based on an 8051 FPGA core. I want to eliminate any unused gates. Are there any opcodes in the 8051 instruction set that your C compiler does not use?

ANSWER

• If you compile your program in ROM(LARGE) and refrain from using an optimization level higher than 6, ACALL and AJMP instructions are not generated.
• If you use ROM(SMALL), LJMP and LCALL instructions are not generated.

The XCHD instruction is not generated by the compiler at this time.

All remaining instructions may be generated by the compiler.

MORE INFORMATION

• Refer to ROM in the Cx51 User's Guide.

Last Reviewed: Thursday, February 25, 2021