november 2010 doc id 18275 rev 1 1/8 AN3321 application note how to enable remote reset from jtag on evalspear310 board rev 2.0 introduction this application note provides information on how to modify the evaluation board for spear310 (evalspear310) rev 2.0 to enable re mote system reset through the jtag interface. remote reset is a feature not available by default on evals pear310 board, but it can help during software debug activity. www.st.com
how to enable the remote system reset from jtag AN3321 2/8 doc id 18275 rev 1 1 how to enable the remote system reset from jtag the evalspear310 board (evb) ha s a standard "multi-ice jt ag interface" connector, named j26. through j26, it is possible to connect a jtag adapter (refer to appendix f of the reference document [ 1. ]). the connector supports separate reset signals for jtag-tap (ntrst pin) and for the board system (nsrst pin). on the evb rev 2.0, the actual circuit for system reset is not able to receive a remote reset from the jtag connector. this can affect th e debugging activity, forcing the developer to reset manually by pressing the on-board reset button. note: 1 all the modifications listed below are mandatory. 2 a basic skill on solder ing tools is required. here below you can find the list of all the modifications required on the evb to enable remote system reset through jtag. before starting, you need the following components: one device p/n stm6315sdw13f one resistor in package 0603, value 0 ohm. it can be replaced with a short wire connection. connecting the nsrst pin of the jtag connector the evb default assembly confi guration has one resistor (r32 9) missing, isolating nsrst pin. to connect nsrst pin: mount the r329 resistor, 0 ohm. it is located close to the jtag connector on the bottom layer. joining all reset signals in a single wire on the revision 2.0 of the board, the reset is distributed through the unidirectional device u12. by design, u12 blocks nsrst signals to go from jtag to system reset, and prevents jtag to reset all on-board components. to connect the nsrst signal to the system reset, modify the top layer of the board as follows (see figure 1: evb top layer ): 1. remove u12, located near the jtag connector. 2. solder together pins 7, 8 and 9 of u12. 3. solder together pins 11, 12, 13, 14, 15, 16, 17 and 18 of u12. figure 3 shows the area of u12 after these modifications. this is an esd sensitive device, improper handling can cause permanent damage to the on-board components.
AN3321 how to enable the remote system reset from jtag doc id 18275 rev 1 3/8 creating a "wired and" reset to comply with jtag specifications, the reset wire has to be a "wired and" of "open drain" devices with a common pull-up resistor. the actual reset chip u11 does not have any "open drain" output. to make this feature available: replace the reset chip u11 with a stm6315sdw13f. u11 is located close to jtag connector on the bottom layer (see figure 2: evb bottom layer ). passive pull-up is already available (r242). cleaning-up reset wire on the actual revision of the board, some optional delay circuits are installed adding high load to reset wire. this is not compliant with jt ag specifications. to solve this issue modify the top layer of the board as follows (see figure 1: evb top layer ): 1. remove r137 and c57, located near the smii phy u18 2. remove r172 and c75, located near the smii phy u19 3. remove r207 and c90, located near the smii phy u20 4. remove c236, located near the smii phy u21. be careful not to remove r242
how to enable the remote system reset from jtag AN3321 4/8 doc id 18275 rev 1 figure 1. evb top layer
AN3321 how to enable the remote system reset from jtag doc id 18275 rev 1 5/8 figure 2. evb bottom layer figure 3. connections replacing u12
references AN3321 6/8 doc id 18275 rev 1 2 references 1. arm, dui 0048 f, user manual "multi-ice" version 2.2 http://infocenter.arm.com/help/topic/com.arm.doc.dui0048f/dui0048.pdf 2. stmicroelectronics, "evalspear310 boar d um - rev. 2" user manual (um0843) http://www.st.com/stonline/products/literature/um/16543.pdf
AN3321 revision history doc id 18275 rev 1 7/8 3 revision history table 1. document revision history date revision changes 25-nov-2010 1 initial release.
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