The DIO Driver accesses Master, Slave and carrier boards through the computer’s bus (See the figure: Two Different DIO Domains on One PC Bus). The driver can accommodate up to 16 masters (from either family) and each master can have up to 7 DIO slave boards. ISA based DIOs and carrier boards have switches to set their base address to identify by the driver where PCI and PXI boards are using the physical slot number they are installed in to identify by the driver. PXI and PCI boards Master and Slave numbers are set through selector switches located on the front.