The DIO Driver accesses Master, Slave and carrier boards through the computer’s bus (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 used to set their base address where PCI and PXI boards are using physical slot numbers that they are installed on in order to identify themselves by the driver. PXI and PCI boards Master and Slave numbers are set through selector switches located on the front.