Immediate Values

A project log for World's first 32bit Homebrew CPU

Creating the world's first 32bit homebrew CPU using 74' series logic.

Phil Wright 10/22/2017 at 23:200 Comments

Many of the RISC-V instructions encode immediate values within the instruction. Converting these encoded values into actual 32 bit values is dependent on the instruction type. There are 6 instruction formats but only 5 contain an immediate value.

Our design spans two boards and takes as input the full 32 bit instruction and control lines indicating the instruction type. (The type is discovered by the decoder elsewhere). The logic is simple enough but not so simple that I avoided a mistake the first time around. Hence the boards are marked as V1.1, as shown below.