diff options
Diffstat (limited to 'src/jtag/jtag.h')
| -rw-r--r-- | src/jtag/jtag.h | 56 |
1 files changed, 33 insertions, 23 deletions
diff --git a/src/jtag/jtag.h b/src/jtag/jtag.h index 4d482f06..2c186e9c 100644 --- a/src/jtag/jtag.h +++ b/src/jtag/jtag.h @@ -248,7 +248,14 @@ extern int jtag_register_commands(struct command_context_s *cmd_ctx); /* JTAG interface, can be implemented with a software or hardware fifo * * TAP_SD and TAP_SI are illegal end states. TAP_SD/SI as end states - * can be emulated by using a larger scan. + * can be emulated by using a larger scan. + * + * Code that is relatively insensitive to the path(as long + * as it is JTAG compliant) taken through state machine can use + * endstate for jtag_add_xxx_scan(). Otherwise the pause state must be + * specified as end state and a subsequent jtag_add_pathmove() must + * be issued. + * */ extern void jtag_add_ir_scan(int num_fields, scan_field_t *fields, enum tap_state endstate); extern int interface_jtag_add_ir_scan(int num_fields, scan_field_t *fields, enum tap_state endstate); @@ -258,30 +265,24 @@ extern void jtag_add_plain_ir_scan(int num_fields, scan_field_t *fields, enum ta extern int interface_jtag_add_plain_ir_scan(int num_fields, scan_field_t *fields, enum tap_state endstate); extern void jtag_add_plain_dr_scan(int num_fields, scan_field_t *fields, enum tap_state endstate); extern int interface_jtag_add_plain_dr_scan(int num_fields, scan_field_t *fields, enum tap_state endstate); -/* execute a state transition within the JTAG standard, but the exact path - * path that is taken is undefined. Many implementations use precisely - * 7 clocks to perform a transition, but it could be more or less - * than that. - * - * The following assertions are made about certain common state moves: - * - * - A state move from Pause-[ID]R to Pause-[ID]R should always go through - * Update-[ID]R and Capture-[ID]R before returning to Pause-[ID]R, otherwise - * there's no way force a register update, if you can't go to Run-Test/Idle for - * some reason. +/* run a TAP_TLR reset. End state is TAP_TLR, regardless + * of start state. + */ +extern void jtag_add_tms(); +extern int interface_jtag_add_tms(); +/* Do not use jtag_add_pathmove() unless you need to, but do use it + * if you have to. * - * - A state move from Pause-[ID]R to Shift-[ID]R must not go through - * Update-[ID]R. + * DANGER! If the target is dependent upon a particular sequence + * of transitions for things to work correctly(e.g. as a workaround + * for an errata that contradicts the JTAG standard), then pathmove + * must be used, even if some jtag interfaces happen to use the + * desired path. Worse, the jtag interface used for testing a + * particular implementation, could happen to use the "desired" + * path when transitioning to/from end + * state. * - * - Run-Test/Idle must not be entered unless requested, because R-T/I may have - * side effects. - * - * NB! a jtag_add_statemove() to the current state is not - * a no-operation. - */ -extern void jtag_add_statemove(enum tap_state endstate); -extern int interface_jtag_add_statemove(enum tap_state endstate); -/* A list of unambigious single clock state transitions, not + * A list of unambigious single clock state transitions, not * all drivers can support this, but it is required for e.g. * XScale and Xilinx support * @@ -289,6 +290,15 @@ extern int interface_jtag_add_statemove(enum tap_state endstate); * * Note that the first on the list must be reachable * via a single transition from the current state. + * + * All drivers are required to implement jtag_add_pathmove(). + * However, if the pathmove sequence can not be precisely + * executed, an interface_jtag_add_pathmove() or jtag_execute_queue() + * must return an error. It is legal, but not recommended, that + * a driver returns an error in all cases for a pathmove if it + * can only implement a few transitions and therefore + * a partial implementation of pathmove would have little practical + * application. */ extern void jtag_add_pathmove(int num_states, enum tap_state *path); extern int interface_jtag_add_pathmove(int num_states, enum tap_state *path); |