Sten <debian@sansys-electronic.com>: add support for ICEbear FDTI-based interface.

[openocd.git] / src / jtag / jtag.h

diff --git a/src/jtag/jtag.h b/src/jtag/jtag.h
index 434320b49546b5e119f7911b697b971366b39d0a..5dfbbdce42ff527bdc219eeaa666c058325ad93b 100644 (file)
--- a/src/jtag/jtag.h
+++ b/src/jtag/jtag.h
@@ -181,6 +181,25 @@ tap_state_t tap_get_end_state(void);
  */
 int tap_get_tms_path(tap_state_t from, tap_state_t to);
 
+
+/**
+ * Function int tap_get_tms_path_len
+ * returns the total number of bits that represents a TMS path
+ * transition as given by the function tap_get_tms_path().
+ *
+ * For at least one interface (JLink) it's not OK to simply "pad" TMS sequences
+ * to fit a whole byte.  (I suspect this is a general TAP problem within OOCD.)
+ * Padding TMS causes all manner of instability that's not easily
+ * discovered.  Using this routine we can apply EXACTLY the state transitions
+ * required to make something work - no more - no less.
+ *
+ * @param from is the starting state
+ * @param to is the resultant or final state
+ * @return int - the total number of bits in a transition.
+ */
+int tap_get_tms_path_len(tap_state_t from, tap_state_t to);
+
+
 /**
  * Function tap_move_ndx
  * when given a stable state, returns an index from 0-5.  The index corresponds to a
@@ -376,7 +395,6 @@ struct jtag_tap_s
 };
 extern jtag_tap_t* jtag_AllTaps(void);
 extern jtag_tap_t* jtag_TapByPosition(int n);
-extern jtag_tap_t* jtag_TapByPosition(int n);
 extern jtag_tap_t* jtag_TapByString(const char* dotted_name);
 extern jtag_tap_t* jtag_TapByJimObj(Jim_Interp* interp, Jim_Obj* obj);
 extern jtag_tap_t* jtag_TapByAbsPosition(int abs_position);
@@ -556,7 +574,18 @@ extern int  interface_jtag_add_plain_dr_scan(int num_fields, scan_field_t* field
 extern void jtag_add_tlr(void);
 extern int  interface_jtag_add_tlr(void);
 
-/* Do not use jtag_add_pathmove() unless you need to, but do use it
+/* Application code *must* assume that interfaces will
+ * implement transitions between states with different
+ * paths and path lengths through the state diagram. The
+ * path will vary across interface and also across versions
+ * of the same interface over time. Even if the OpenOCD code
+ * is unchanged, the actual path taken may vary over time
+ * and versions of interface firmware or PCB revisions.
+ * 
+ * Use jtag_add_pathmove() when specific transition sequences
+ * are required.
+ * 
+ * Do not use jtag_add_pathmove() unless you need to, but do use it
  * if you have to.
  *
  * DANGER! If the target is dependent upon a particular sequence