Each block is briefly described below. For more detail, see the HDL source code. The instruction decoder controls the operation of the V8. It fetches instructions from memory and loads them into the opcode register. After decoding the instruction, the decoder outputs the appropriate control signals.
Interrupt processing depends on the type of interrupt.
The ALU block performs the 8-bit arithmetic and logical operations. Certain constants, such as 0 and 1, can also be selected as inputs to the ALU for increment and decrement operations. The ALU includes bit-manipulation logic to allow the testing, setting, and clearing of a single bit in a byte. Most opcodes pass data through the ALU so it can update the appropriate PSR flags. The registers are named R0 through R7.