Microcode builder for Atto-8 microprocessor
The microcode builder is a tool for generating microcode for the Atto-8 microprocessor. It outputs a microcode image file to argv[1] which is exactly 0x2000 words in size. The microcode builder adheres to the Atto-8 microprocessor specification as defined in /spec/microprocessor.md.
Unofficial opcode 0xBB is mapped to unofficial control word 0xFFFC for debug requests.
The fetch cycle assumes that YL is set to 0x00, which allows it to be significantly shorter. Consequently, every instruction must reset YL to 0x00 before clearing SC and fetching the next instruction.
Microcode branches are performed by matching against CF and microcode loops are performed by setting SC to 0x00 through CLR_SC.