diff options
| -rw-r--r-- | src/jtag/dummy.c | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/src/jtag/dummy.c b/src/jtag/dummy.c index f6ca87c2..a3a0a1aa 100644 --- a/src/jtag/dummy.c +++ b/src/jtag/dummy.c @@ -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 @@ int dummy_read(void) 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 @@ int dummy_quit(void) 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;
+}
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