A DIO domain has one Master DIO board and up to seven DIO Slave boards. A DIO domain is comprised of a Master and Slave cards. The figure below shows two domains from two different families on a PC bus.
Two Different DIO Domains on One PC Bus
Domains are internally synchronized and controlled from the Master via the PXI backplane.
Masters and slaves within a domain must be members of the same product family. Each Slave adds 32 additional UUT I/O channels. Up to seven slaves can be added to a domain.
A full domain containing eight DIO boards provides 256 UUT I/O channels (256 channels wide). Because the driver supports up to 16 masters, up to 16 domains of can be supported. The number of master/slaves depends on the total number of PXI slots available in your system.