What good is a cpu without an assembler? In this chapter we use flex and bison (i.e. lex and yacc) to make an assembler for our cpu. The assembler generates a binary file that can be loaded by the verilog $readmemh statement, or in a synthesized FPGA we would use the binary file to initialize the instruction memory inside the FPGAs internal memory blocks.
Before we move on to updating our basic cpu verilog code let us talk a little more about the four basic units of a cpu. These parts are typically called the Datapath, Function Unit or ALU, Memory/Register File and the Control Unit. Any cpu must at least have these four basic blocks.
In this first chapter we learn the very basics of a CPU's core logic. We include basic Function Unit logic such as logical operators and math functions. To keep our first chapter simple, branching is not yet implemented so our programs are strictly linear and cannot include loop constructs. Also, the program code is included directly in the CPU source file.
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Your First CPU