User manual

Chapter 4 VXI-MXI-2/B Configuration and Installation

VXIbus Logical Address

Each device in a VXIbus/MXIbus system is assigned a unique number

between 0 and 254. This 8-bit number, called the logical address,

defines the base address for the VXI configuration registers located on

the device. With unique logical addresses, each VXIbus device in the

system is assigned 64 bytes of configuration space in the upper 16 KB

of A16 space.

Logical address 0 is reserved for the Resource Manager in the VXIbus

system. Because the VXI-MXI-2/B cannot act as a Resource Manager,

do not configure the VXI-MXI-2/B with a logical address of 0.

Some VXIbus devices have dynamically configurable logical

addresses. These devices have an initial logical address of hex FF or

255, which indicates that they can be dynamically configured. While

the VXI-MXI-2/B does support dynamic configuration of VXI devices

within its mainframe, it is itself a statically configured device and is

preset at the factory with a VXI logical address of 1.

Ensure that no other statically configurable VXIbus devices have a

logical address of 1. If they do, change the logical address setting of

either the VXI-MXI-2/B or the other device so that every device in the

system has a unique associated logical address.

You can change the logical address of the VXI-MXI-2/B by changing

the setting of the 8-bit DIP switch at location designator U20 (See

Figure 4-1). The ON position of the DIP switch corresponds to a logic

value of 0 and the OFF position corresponds to a logic value of 1.

Verify that the VXI-MXI-2/B does not have the same logical address as

any other statically configured VXIbus device in your system.

Remember that logical addresses hex 0 and FF are not allowed for the

VXI-MXI-2/B. Also, when setting logical addresses, keep in mind the

grouping requirements set by the system hierarchy. See Chapter 6,

System Configuration, or VXI-6, VXIbus Mainframe Extender

Specification, for more information on setting logical addresses on a

multimainframe hierarchy.