The Silicon Labs IDE does not support the LX51 linker, only the the BL51 linker.

However, the LX51 linker may be used with µVision for projects less than 64k that do not require code banking.

The LX51 linker code packing option may result in a 3-8% code size reduction.

To use the LX51 linker with µVision and enable code packing:

• Open Keil µVision
• Select Options for Target from the Project Menu
• Click on the first tab labeled Device
• Check Use Extended Linker (LX51) instead of BL51 linker
• Also check Use Extended Assembler (AX51) instead of A51
• Click on the C51 tab
• Check the Linker Code Packing optimization

When linking more than 64kB of program code on devices that use code banking, the BL51 linker must be used.