-<p>An implementation of the T-Frame can be found in tinyos-2.x/tos/chips/cc2420.</p>
-<p>An implementation of the I-Frame can be found in tinyos-2.x/tos/chips/cc2420.</p>
+<p>An implementation of T-Frames and I-Frames can be found in
+tinyos-2.x/tos/chips/cc2420/. The components in
+tos/chips/cc2420/lowpan/ control which is used. By default, TinyOS
+802.15.4 stacks use I-Frames, and the 'tframe' make option configures
+them to use T-Frames. This make option defines a symbol named
+<tt class="docutils literal"><span class="pre">TFRAMES_ENABLED</span></tt>. In the case of the CC2420 stack, this causes
+<tt class="docutils literal"><span class="pre">CC2420.h</span></tt> to define <tt class="docutils literal"><span class="pre">CC2420_IFRAME_TYPE</span></tt>, which adds the extra
+byte to the message_t header structure.</p>