From db4fe036131b5f1751bc46b2b79b7139210a6df9 Mon Sep 17 00:00:00 2001 From: drath Date: Sun, 24 Feb 2008 18:24:04 +0000 Subject: [PATCH] - concretize JTAG state transition rules (previously implied behaviour is now documented) git-svn-id: svn://svn.berlios.de/openocd/trunk@329 b42882b7-edfa-0310-969c-e2dbd0fdcd60 --- src/jtag/jtag.h | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/src/jtag/jtag.h b/src/jtag/jtag.h index f70c1ead8..e5df6619b 100644 --- a/src/jtag/jtag.h +++ b/src/jtag/jtag.h @@ -248,11 +248,24 @@ extern int jtag_add_ir_scan(int num_fields, scan_field_t *fields, enum tap_state extern int jtag_add_dr_scan(int num_fields, scan_field_t *fields, enum tap_state endstate, void *dummy_anachronism); extern int jtag_add_plain_ir_scan(int num_fields, scan_field_t *fields, enum tap_state endstate, void *dummy_anachronism); extern int jtag_add_plain_dr_scan(int num_fields, scan_field_t *fields, enum tap_state endstate, void *dummy_anachronism); -/* execute a state transition within the JTAG standard, but nothing is defined - * w.r.t. the path that is taken. Many implementations use precisely +/* 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. + * + * - A state move from Pause-[ID]R to Shift-[ID]R must not go through + * Update-[ID]R. + * + * - Run-Test/Idle must not be entered unless requested, because R-T/I may have + * side effects. + */ extern int jtag_add_statemove(enum tap_state endstate); /* A list of unambigious single clock state transitions, not * all drivers can support this, but it is required for e.g.