The PIO-D64 provides 32 digital input channels, 32 output channels and 6 counter/timer channels. The PIO-D64 consists of two 16-bit input ports and two 16-bit output ports. Users can use the DB-16P to connect the input ports (CN2 and CN4) for isolation purposes. The DB-16R can be used to interface the output ports (CN1 and CN3) for relay control. There are four-clock sources: 2M, 1M, 500K and 250K on the board; users can use the clock sources from the soldering pad. The on board timer / counter provides 3 channels for frequency measurement, event counting and pulse generation. The second 8254 provides 3 channels for interrupt function. It can be installed in a 5V PCI bus and can support true "Plug & Play".