Where bytevalue is a value between 0 and 255 that sets the desired bit pattern. The following information defines common base addresses for port registers. Note that the register bits are listed as well as the corresponding DB25 connector pin that that bit is connected to. All the lines listed as Outputs are open collector type on most newer computers, which means that with care they can be used as inputs. BASE ADDRESS (PDR) Data register (Read or Write) Bit 0 Pin 2 Data Output Bit 1 Pin 3 Data Output Bit 2 Pin 4 Data Output Bit 3 Pin 5 Data Output Bit 4 Pin 6 Data Output Bit 5 Pin 7 Data Output Bit 6 Pin 8 Data Output Bit 7 Pin 9 Data Output BASE ADDRESS + 1 (PSR) Status register.