Cause: MDK 5.30 and above omit AC5 by default.
Solution: You must manually add AC5 via the Pack Installer:
Keil ARM Compiler Version 5 (often referred to as ARMCC or RVCT-derived) is a legacy C/C++ compiler toolchain for ARM-based microcontrollers. It was the default compiler for Keil MDK (Microcontroller Development Kit) for many years before being replaced by Arm Compiler 6 (based on LLVM/clang). keil arm compiler version 5 download
Despite being officially deprecated, version 5 remains widely used in industries requiring long-term stability, legacy codebases, or specific certified software (e.g., functional safety applications). Cause: MDK 5
Cause: Arm Compiler 5 generates DWARF 2 debug info by default. Some newer debug probes (e.g., certain J-Link versions) expect DWARF 4. After logging in, go to: Downloads → Keil
Solution: In µVision, go to Target Options → C/C++ tab → Misc Controls and add --dwarf=3 to force a compatible level.
After logging in, go to: Downloads → Keil MDK → Legacy Versions
Alternatively, use this direct URL structure (subject to change, but historically stable):
https://www.keil.com/download/product/