+ *
+ * From the XSVF spec, pertaining to XSTATE:
+ *
+ * For special states known as stable states (Test-Logic-Reset,
+ * Run-Test/Idle, Pause-DR, Pause- IR), an XSVF interpreter follows
+ * predefined TAP state paths when the starting state is a stable state
+ * and when the XSTATE specifies a new stable state. See the STATE
+ * command in the [Ref 5] for the TAP state paths between stable
+ * states.
+ *
+ * For non-stable states, XSTATE should specify a state that is only one
+ * TAP state transition distance from the current TAP state to avoid
+ * undefined TAP state paths. A sequence of multiple XSTATE commands can
+ * be issued to transition the TAP through a specific state path.
+ *
+ * @note Unless @a tms_bits holds a path that agrees with [Ref 5] in *
+ * above spec, then this code is not fully conformant to the xsvf spec.
+ * This puts a burden on tap_get_tms_path() function from the xsvf spec.
+ * If in doubt, you should confirm that that burden is being met.
+ *
+ * Otherwise, state must be immediately reachable in one clock cycle,
+ * and does not need to be a stable state.