On Mon, Sep 14, 2009 at 10:08 PM, Johannes Stezenbach <j...@sig21.net> wrote: > On Mon, Sep 14, 2009 at 08:35:32PM +0200, Øyvind Harboe wrote: >> On Mon, Sep 14, 2009 at 7:42 PM, David Brownell <davi...@pacbell.net> wrote: >> > On Monday 14 September 2009, Ųyvind Harboe wrote: >> >> I suspect there are JTAG controllers that do not communicate when >> >> SRST is asserted, but do not pull TRST. >> >> >> >> srst_pulls_trst will kinda work on these devices i.MX27(??). >> >> >> >> The first thought that strikes me here is to split out srst_pulls_trst >> >> into >> >> two flags: pulls trst and no JTAG communication during srst.... >> > >> > What code do we have which wants JTAG chitchat during SRST? >> >> I thought arm7/9 did this, but I was wrong. I'm wondering if >> XScale needs this. >> >> Turns out after some more testing that i.MX27 does appear to >> pull trst during srst. > > I thought the desired reset procedure at least on ARM9 is: > > - pull SRST and TRST (TRST not only resets the TAP but also EmbeddedICE) > - release TRST > - program EmbeddedICE to break on reset vector > - release SRST
To optionally program arm7/9 if srst does not gate the JTAG clock is a possible improvement, but I'm not sure why it would be better to program EmbeddedICE to break on reset vector while srst is asserted. What would that achieve as oposed to first programming the break on reset and afterwards asserting/deasserting srst? > There are SoCs where SRST gates the ARM core clock, thus you > cannot program EmbeddedICE while SRST is asserted; then you need: > > - pull SRST and TRST > - release SRST and TRST > - program EmbeddedICE to break on reset vector > - pull SRST again > - release SRST The three last steps are indeed followed by OpenOCD. Additionally if srst pulls trst -- Øyvind Harboe Embedded software and hardware consulting services http://www.zylin.com _______________________________________________ Openocd-development mailing list Openocd-development@lists.berlios.de https://lists.berlios.de/mailman/listinfo/openocd-development
