This patch adds JTAG state tracking to dummy.c
It deliberately use logic different from the lookup table that any
calling code would use, so as to verify the state transitions with
another point of view.
I also introduce the typedef for enum tap_state as tap_state_t which is
one word shorter.
The means of the logging and printing of the state transitions is
debatable. I don't care, this can be easily commented out by someone
who is annoyed by it.
Dick
Index: src/jtag/dummy.c
===================================================================
--- src/jtag/dummy.c (revision 1261)
+++ src/jtag/dummy.c (working copy)
@@ -26,6 +26,15 @@
#include "jtag.h"
#include "bitbang.h"
+
+/* my private tap controller state, which tracks state for calling code */
+static tap_state_t dummy_state = TAP_RESET;
+
+static int dummy_clock; /* edge detector */
+
+static tap_state_t tap_state_transition(tap_state_t cur_state, int tms);
+
+
int dummy_speed(int speed);
int dummy_register_commands(struct command_context_s *cmd_ctx);
int dummy_init(void);
@@ -70,12 +79,28 @@
return 1;
}
+
void dummy_write(int tck, int tms, int tdi)
{
+ /* TAP standard: "state transitions occur on rising edge of clock" */
+ if( tck != dummy_clock )
+ {
+ if( tck )
+ {
+ int old_state = dummy_state;
+ dummy_state = tap_state_transition( dummy_state, tms );
+ if( old_state != dummy_state )
+ LOG_INFO( "dummy_tap=%s", jtag_state_name(dummy_state) );
+ }
+ dummy_clock = tck;
+ }
}
void dummy_reset(int trst, int srst)
{
+ dummy_clock = 0;
+ dummy_state = TAP_RESET;
+ LOG_DEBUG( "reset to %s", jtag_state_name(dummy_state) );
}
static int dummy_khz(int khz, int *jtag_speed)
@@ -130,3 +155,107 @@
void dummy_led(int on)
{
}
+
+
+/**
+ * Function tap_state_transition
+ * takes a current TAP state and returns the next state according to the tms value.
+ *
+ * Even though there is code to duplicate this elsewhere, we do it here a little
+ * differently just to get a second opinion, i.e. a verification, on state tracking
+ * in that other logic. Plus array lookups without index checking are no favorite thing.
+ * This is educational for developers new to TAP controllers.
+ */
+static tap_state_t tap_state_transition(tap_state_t cur_state, int tms)
+{
+ tap_state_t new_state;
+
+ if (tms)
+ {
+ switch (cur_state)
+ {
+ case TAP_RESET:
+ new_state = cur_state;
+ break;
+ case TAP_IDLE:
+ case TAP_DRUPDATE:
+ case TAP_IRUPDATE:
+ new_state = TAP_DRSELECT;
+ break;
+ case TAP_DRSELECT:
+ new_state = TAP_IRSELECT;
+ break;
+ case TAP_DRCAPTURE:
+ case TAP_DRSHIFT:
+ new_state = TAP_DREXIT1;
+ break;
+ case TAP_DREXIT1:
+ case TAP_DREXIT2:
+ new_state = TAP_DRUPDATE;
+ break;
+ case TAP_DRPAUSE:
+ new_state = TAP_DREXIT2;
+ break;
+ case TAP_IRSELECT:
+ new_state = TAP_RESET;
+ break;
+ case TAP_IRCAPTURE:
+ case TAP_IRSHIFT:
+ new_state = TAP_IREXIT1;
+ break;
+ case TAP_IREXIT1:
+ case TAP_IREXIT2:
+ new_state = TAP_IRUPDATE;
+ break;
+ case TAP_IRPAUSE:
+ new_state = TAP_IREXIT2;
+ break;
+ default:
+ LOG_ERROR( "fatal: invalid argument cur_state=%d", cur_state );
+ exit(1);
+ break;
+ }
+ }
+ else
+ {
+ switch (cur_state)
+ {
+ case TAP_RESET:
+ case TAP_IDLE:
+ case TAP_DRUPDATE:
+ case TAP_IRUPDATE:
+ new_state = TAP_IDLE;
+ break;
+ case TAP_DRSELECT:
+ new_state = TAP_DRCAPTURE;
+ break;
+ case TAP_DRCAPTURE:
+ case TAP_DRSHIFT:
+ case TAP_DREXIT2:
+ new_state = TAP_DRSHIFT;
+ break;
+ case TAP_DREXIT1:
+ case TAP_DRPAUSE:
+ new_state = TAP_DRPAUSE;
+ break;
+ case TAP_IRSELECT:
+ new_state = TAP_IRCAPTURE;
+ break;
+ case TAP_IRCAPTURE:
+ case TAP_IRSHIFT:
+ case TAP_IREXIT2:
+ new_state = TAP_IRSHIFT;
+ break;
+ case TAP_IREXIT1:
+ case TAP_IRPAUSE:
+ new_state = TAP_IRPAUSE;
+ break;
+ default:
+ LOG_ERROR( "fatal: invalid argument cur_state=%d", cur_state );
+ exit(1);
+ break;
+ }
+ }
+
+ return new_state;
+}
Index: src/jtag/jtag.h
===================================================================
--- src/jtag/jtag.h (revision 1261)
+++ src/jtag/jtag.h (working copy)
@@ -35,14 +35,14 @@
/* 16 Tap States, from page 21 of ASSET InterTech, Inc.'s svf.pdf
*/
-enum tap_state
+typedef enum tap_state
{
TAP_RESET = 0x0, TAP_IDLE = 0x8,
TAP_DRSELECT = 0x1, TAP_DRCAPTURE = 0x2, TAP_DRSHIFT = 0x3, TAP_DREXIT1 = 0x4,
TAP_DRPAUSE = 0x5, TAP_DREXIT2 = 0x6, TAP_DRUPDATE = 0x7,
TAP_IRSELECT = 0x9, TAP_IRCAPTURE = 0xa, TAP_IRSHIFT = 0xb, TAP_IREXIT1 = 0xc,
TAP_IRPAUSE = 0xd, TAP_IREXIT2 = 0xe, TAP_IRUPDATE = 0xf
-};
+} tap_state_t;
typedef struct tap_transition_s
{
@@ -530,7 +530,7 @@
/**
* Function jtag_state_name
- * Returns a string suitable for display representing the JTAG tap_state
+ * Returns a string suitable for display representing the JTAG tap_state
*/
const char* jtag_state_name(enum tap_state state);
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