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10.0 FEP Management

10.1 Overview

This section describes the preliminary design of the ACIS Back End's FEP (Front End Processor) Management software. This software is responsible for loading science code and data into the Front End Processors, issuing commands to the Front End Processors, and for acquiring data produced by the processors.

10.2 FEP Code and Data Loads

The format and content of Front End Code and Data loads are TBD. They will probably consist of a destination address, length, and data. The structure will probably contain one or more blocks, where each block has a FEP selection mask, FEP destination virtual address, the length of the load, and the data to load. The data will consist of a series of 32-bit words, formatted using little-endian byte ordering.

10.3 FEP Management

10.3.1 Overview

Figure 13 illustrates a simplified data acquisition scenario for the FEP.

FIGURE 13. FEP Management Scenario

10.3.2 FEP Management - Class "FEP Manager"

The Back End software manages Front End commanding and data acquisition using a FEP Manager class. This class is responsible for fielding requests to the Front End Processors, and for acquiring and dispatching data produced by the Front Ends. All I/O operations to and from the Front Ends are performed via the "FEP Device" (see Table 9, "`DEA Device' Operations," on page 35). Table 31 lists the operations provided by the FEP Manager.

TABLE 31. `FEP Manager'Operations

Function                     Inputs                                   Outputs                     
Initialize                   Address of "FEP Device" to use for       none                        
                             input and output.                                                    
                             TBD: If each FEP has its own device,                                 
                             then this should be an array of "FEP                                 
                             Devices," with the array index serving                               
                             as the FEP Identifier.                                               
FEP Reset                    FEP Identifier                           none (Pulses the FEP's      
                                                                      Reset line)                 
FEP Disable                  FEP Identifier                           none (This takes the        
                                                                      indicated FEP off-line)     
Write FEP Memory             FEP Identifier                           none (Loads the FEP's       
                             FEP Address to write                     memory with the speci       
                             Length to write                          fied data)                  
                             Data to write                                                        
Read FEP Memory              FEP Identifier                           Fills "Destination          
                             FEP Address to read                      Buffer" with the            
                             Length to Read                           requested FEP Data          
                             Destination Buffer                                                   
Execute FEP Memory           FEP Identifier                           Tell the FEP to call the    
                             FEP Address to Execute                   function located at the     
                             Reply Buffer                             indicated memory loca       
                             TBD: Time-out Value                      tion. Once the called       
                                                                      function returns, the       
                                                                      return value is stored in   
                                                                      "Reply Buffer."             
Run FEP                      FEP Identifier                           Tell the FEP to execute     
                             FEP Address to Execute                   the code loaded at the      
                                                                      specified memory loca       
                                                                      tion. This code is          
                                                                      expected to run until       
                                                                      the FEP is reset.           
Get FEP Status               FEP Identifier                           Reports the current         
                                                                      state of the indicated      
Acquire FEP Data             Destination Buffer                       Waits for data from any     
                             Max. Length                              of the running FEPs.        
                             TBD: Time-out Value                      Once data arrives,          
                                                                      "Destination Buffer" is     
                                                                      filled with the FEP gen     
                                                                      erated information.         
Dump FEP Memory (TBD)        FEP Identifier                           Acquires and teleme         
                             FEP Address to read                      ters the requested infor    
                             Length to Read                           mation from the             
                                                                      specified FEP.              
Execute FEP Memory and Tele  FEP Identifier                           Cause the FEP to call       
meter Reply (TBD)            FEP Address to Execute                   the specified code, then    
                             TBD: Time-out Value                      wait for and telemeter      
                                                                      the response.               

Whether or not the FEP Manager is responsible for forming the telemetry responses to "Dump Memory" and "Execute Memory" commands is TBD.


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