Target Language Compiler

Caution Against Directly Accessing Record Fields

When functions in the block target file are called, they are passed the block and system records for this instance as arguments. The first argument, block, is in scope, which means that variable names inside this instances Block record are accessible by name. For example,

%assign fast = SFcnParamSetting.Fast

Block target files could generate code for a given block by directly using the fields in the Block record for the block. This process is not recommended for two reasons:

• The contents of the model.rtw file can change from release to release. This can cause block TLC files that access the model.rtw file directly to no longer work.
• TLC library functions are provided that substantially reduce the amount of TLC code needed to implement a block while handling all the various configurations (widths, data types, etc.) a block might have. These library functions are provided by the system target files to provide access to inputs, outputs, parameters, and so on. Using these functions in a block ensures it is written to be flexible enough to generate code for any instance/configuration of the block and across releases. An exception is when it is necessary to access directly a field in the Block's record. This is for Parameter Settings, which is discussed below.

Using Library Functions to Access model.rtw Contents

Exception to Using the Library Functions