cdsParameters.md

@@ -158,3 +158,19 @@ These options are supported, but don't get a lot of use.
 - `lhomid`
     - Adds an additional second to the system time on startup.
     - Was used for LHO pemmid
+
+# Overriding cdsParameters at Build Time
+Because the parameters cause differing static code to be emitted for the model, the parameters can only be overridden at build time. The `RCG_OVERRIDE_CDS_PARAMETERS` can be used to accomplish this. This capability is mostly used for librts and test system builds, being useful for changing things like the model rate, vectorization, etc.
+
+## Usage
+### `rtcds`
+Export or set the `RCG_OVERRIDE_CDS_PARAMETERS` 
+```sh
+$ RCG_OVERRIDE_CDS_PARAMETERS="host=x1cymac:ifo=X1:rate=2K:dcuid=11:requireIOcnt=0" rtcds build x1tst
+```
+
+### `librts`
+```
+~/advligorts/src/librts$ RCG_OVERRIDE_CDS_PARAMETERS="host=x1cymac:ifo=X1:rate=16K:dcuid=11:requireIOcnt=0" make x1unittest
+```
+