The program counter module is split between two different boards because there are too many IC's to fit on a single 100mm x 80mm sized board. The top board provides storage by using 4 x 74HC574 IC's that each store 8 bits. Every clock cycle the storage is updated with the incoming 32-bit address. Because our CPU design is single cycle the PC needs updating every cycle. Hence there is no need for a control line that determines if the PC needs updating during the next tick.

The current value is constantly output to a long header that is connected to the bottom board. This uses 8 x 74HC283 IC's to perform an add of the constant value 4. Because we are implementing the RV32E specification we know it does not need to support the condensed instructions, therefore all instructions are aligned on a 4-byte boundary. Moving to the next instruction always involves adding 4 to the current value. The CPU design will include multiplexors that determine how the input is provided to the PC. It could be the result of adding 4 but it could be the result of a conditional branch or the destination of a jump.