How Can I Configure Logical Addresses of a Multi-Chassis VXI-MXI-2 System?Hardware: VXI/VME/MXI>>MXI Interfaces>>PCI-MXI-2
Problem: How can I configure logical addresses of a multi-chassis VXI-MXI-2 system? Solution: The answer of this question depends on how you would like to configure your system. The possible configurations are daisy chained, in a star configuration via daisy-chaining MXI-2 cables , or any combination of these two. MXI-2 daisy-chaining cables use part numbers 777164-xx, 777165-xx and 777166-xx. The most important aspect to remember is that the NI Resource Manager requires that the first MXI-2 controller must have a logical address (LA) which is a power of two. For example, 1, 2, 4, 8, 16, 32, 64, or 128 are all possible LAs of the first VXI-MXI-2 module attached to the PCI or PXI MXI-2 Controller. DAISY CHAINED CHASSIS SYSTEM Note: A daisy chained chassis system is one where each VXI-MXI-2 is connected to a single MXI-2 cable. Thus, incorporating another VXI chassis would require the addition of a second VXI-MXI-2 board in the original chassis. If your VXI system consists of several VXI chassis each containing more than one MXI-2 module, the LA of the first VXI-MXI-2 may be any of the above suggested LAs, including 1. A LA of 1 will reserve all LAs, up to 255, for this chassis and the children of this chassis, therefore you will not be able to star configure any chassis off of this first chassis. For example, if you have a three chassis system, and Chassis 1 has a VXI-MXI-2 module in slot zero with a LA of 1, you can have another VXI-MXI-2 module in Chassis 1 with a LA higher than that of the instrument LAs in Chassis 1. Chassis 2's VXI-MXI-2 module should then have an LA greater than the second VXI-MXI-2 module in Chassis 1, and Chassis 3 may be controlled by another VXI-MXI-2 module in Chassis 2 in a similar manner. In this case it is not a supported application to star configure any more VXI-MXI-2 modules by piggy-backing another MXI-2 cable into the cable in the VXI-MXI-2 of Chassis 1. In order to star configure more chassis in this way, it is necessary to have the first VXI-MXI-2 module from the PCI-MXI-2 or PXI-MXI-2 controller set to a LA which is a power of 2 and greater than 1, and also follow the guidelines below regarding star configuring chassis via piggy-backed cables. STAR CONFIGURED CHASSIS SYSTEM VIA PIGGY-BACKED MXI-2 CABLES Another way to connect several VXI chassis with VXI-MXI-2 modules is to piggy-back the cables using our right-angle MXI-2 cables and to have only one VXI-MXI-2 module in each chassis. In order to do this, we will want to use a LA that is a power of 2 and greater than 1 for the VXI-MXI-2 module in the first chassis. Some things that are important to remember are that the LA of the first slot zero VXI-MXI-2 module will determine the range of logical address that will be available in this chassis, and that the range of logical addresses reserved for this chassis must be a power of two. For example, if the LA of the VXI-MXI-2 module in the first chassis is 8, there will be any power of 2 up to a maximum of 8 LAs reserved for this particular chassis and its daisy-chained children (see "NOTES" below). If it were 64, there would be any power of 2 up to 64 logical addresses reserved for this chassis and its children. In this configuration, the second and subsequent chassis that are connected in this piggy-backed style can have any LA that permits a quantity of LAs that is a power of two to be reserved for the previous chassis. A three chassis system in a star configuration could have the first chassis' VXI-MXI-2 module set to a logical address of 32, the second chassis's VXI-MXI-2 module set to a LA of 48 (or any LA that is a power of 2 greater than the first), and the third chassis' VXI-MXI-2 module set to a LA of 56. This setup allows a quantity of LAs that is a power of 2 to be reserved for the instruments in each chassis. This gives:
NOTES Let us assume that all three chassis in the star configured example above are five slot chassis and each instrument in the chassis only takes one logical address. It may seem that the logical addresses from 37 to 47 are wasted. This does not have to be the case, it is possible for each chassis in this setup to have other chassis as children. The children of these chassis can be daisy chained as in the first system type discussed above to the chassis that are star configured as long as the instruments in these children chassis don't have logical addresses that extend past the logical addresses reserved for their parent chassis. For more information please refer to the VXI Bus System Specification available at the VXI Consortium webpage. Related Links: Attachments:
Report Date: 11/21/2002 Last Updated: 01/23/2003 Document ID: 2RK9LEUD |
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