Instrument Control Toolbox

The VXI Interface

The VXI interface is associated with a VXI controller that you install in slot 0 of a VXI chassis. This interface, along with the other relevant hardware, is shown below.

The VXI interface is supported through a VISA-VXI object. Many of the features associated with a VISA-VXI object are similar to the features associated with other instrument objects. Therefore, only functions and properties that are unique to VISA's VXI interface are discussed in this section. These unique features are associated with

• Creating a VISA-VXI object
• The VISA-VXI address
• Register-based communication

Refer to Controlling GPIB Instruments to learn about general toolbox capabilities such as writing and reading text and binary data, using events and callbacks, and so on.

Creating a VISA-VXI Object

You create a VISA-VXI object with the visa function. Each object is associated with

• A VXI chassis
• A VXI controller in slot 0 of the VXI chassis
• An instrument installed in the VXI chassis

visa requires the vendor name and the resource name as input arguments. The vendor name is either agilent or ni. The resource name consists of the VXI chassis index and the instrument logical address. You can find the VISA-VXI resource name for a given instrument with the configuration tool provided by your vendor, or with the instrhwinfo function. As described in Configuring Properties During Object Creation, you can also configure property values during object creation.

For example, to create a VISA-VXI object associated with a VXI chassis with index 0 and an Agilent E1432A 16-channel digitizer with logical address 32:

• vv = visa('agilent','VXI0::32::INSTR');
  

The VISA-VXI object vv now exists in the MATLAB workspace. You can display the class of vv with the whos command.

• whos vv
    Name      Size         Bytes  Class
  
    vv        1x1            634  visa object
  
  Grand total is 13 elements using 634 bytes
  

After you create the VISA-VXI object, the properties listed below are automatically assigned values. These properties provide descriptive information about the object based on its class type and address information.

Table 4-3: VISA-VXI Descriptive Properties 

Property Name	Description
Name	Specify a descriptive name for the VISA-VXI object.
RsrcName	Indicate the resource name for a VISA instrument.
Type	Indicate the object type.

You can display the values of these properties for vv with the get function.

• get(vv,{'Name','RsrcName','Type'})
  ans = 
      'VISA-VXI0-32'    'VXI0::32::INSTR'    'visa-vxi'
  

The VISA-VXI Object Display

The VISA-VXI object provides you with a convenient display that summarizes important address and state information. You can invoke the display summary these three ways:

• Type the VISA-VXI object at the command line.
• Exclude the semicolon when creating a VISA-VXI object.
• Exclude the semicolon when configuring properties using the dot notation.

The display summary for the VISA-VXI object vv is given below.

• VISA-VXI Object Using AGILENT Adaptor : VISA-VXI0-32
  
  Communication Address 
     ChassisIndex:       0
     LogicalAddress:     32
  
  Communication State 
     Status:             closed
     RecordStatus:       off
  
  Read/Write State  
     TransferStatus:     idle
     BytesAvailable:     0
     ValuesReceived:     0
     ValuesSent:         0
  

The VISA-GPIB Address

The VISA-VXI Address