8 bit computer, ALU complete
Everything is connected now on the ALU board.
- the bus has been connected (blue wires)
- the A register is connected to the ALU chips (purple wires)
- the B register is connected to the ALU chips (green wires)
- the ALU output is connected to the connector (grey wires)
- the output of the B register is connected to the top connector (coloured flatcable)
First ALU test
The ALU has undergone it’s first limited test (one addition and one subtraction). The A register contained b’00000100′, which is decimal 4 and the B register contained b’00010100′, which is decimal 20.
The addition A plus B yielded b’00011000′ (decimal 24) and the subtraction A minus B gave us b’11101111′ (decimal -16 when in 2’s complement).
Yeah! So far so good.