{"id":13,"date":"2008-05-07T21:30:49","date_gmt":"2008-05-08T02:30:49","guid":{"rendered":"https:\/\/blogs.mathworks.com\/seth\/2008\/05\/07\/bus-signals-in-the-generated-code\/"},"modified":"2008-05-07T22:05:57","modified_gmt":"2008-05-08T03:05:57","slug":"bus-signals-in-the-generated-code","status":"publish","type":"post","link":"https:\/\/blogs.mathworks.com\/simulink\/2008\/05\/07\/bus-signals-in-the-generated-code\/","title":{"rendered":"Bus Signals in the Generated Code"},"content":{"rendered":"

Blog reader Paul\r\nJ. shared<\/a> with us his mental model of the bus as a structure. While this\r\nisn\u2019t true of virtual buses, it is precisely true of nonvirtual buses. In\r\nfact, when you generate the code for a nonvirtual bus using Real-Time Workshop<\/a>, the\r\nresult is a structure.<\/p>\r\n\r\n

Focus on the boundaries<\/strong><\/p>\r\n\r\n

In a previous\r\npost about nonvirtual bus signals<\/a> I talked about memory allocated for the\r\nbus. The places we have to think about memory allocation are the boundaries of\r\nsystems. Here is the simplebusdemo_nv.mdl<\/a><\/p>\r\n\r\n

<\/p>\r\n\r\n

This model has the root level boundaries defined by the\r\ninport and outport blocks. It also has a boundary at the edge of the ReusableFcn\r\nsubsystem. The main_bus crosses this boundary and the generated code is\r\ndifferent if the bus is virtual versus nonvirtual.<\/p>\r\n\r\n

The ReusableFcn subsystem contains a Bus Selector and two\r\ngain blocks.<\/p>\r\n\r\n

<\/p>\r\n\r\n

I configured the subsystem to generate a reusable function. \r\nHere are the settings for the subsystem:<\/p>\r\n\r\n

<\/p>\r\n\r\n

Basically, I have specified how Real-Time Workshop should\r\nwrap up the algorithm implemented inside this system. By specifying \u201cTreat as\r\natomic unit\u201d, the blocks inside the system execute together. Real-Time\r\nWorkshop will generate reusable function code with my specified name\r\n(ReusableFcn) into a file of the same name (ReusableFcn.c). The reusable\r\nfunction code will pass input and output signals as arguments to the function. \r\n<\/p>\r\n\r\n

I can now picture what this will look like:<\/p>\r\n\r\n

ReusableFcn(inputs..., outputs...)<\/PRE><\/p>\r\n\r\n
Virtual buses pass every element separately<\/strong><\/p>\r\n\r\n
<\/p>\r\n\r\n
When the bus signal is virtual at the inport to the\r\nReusableFcn, only the elements of the bus that are used in the system need to\r\nbe passed through the boundary.  Here is the actual code for the function call:<\/p>\r\n\r\n