On Wednesday 10 June 2009, David Brownell wrote:
> http://tiexpressdsp.com/index.php/ICEPICK
>
> The "how to add devices to an ICEpick-C scan chain" highlights
> one point: the JRC commands to add the ARM (and, for DaVinci,
> the ETB) to the scan chain must be done each time the TAPs go
> to the RESET state (via TMS or nTRST).
Hmm, and also:
Before starting the debugger, the debug power domain must
be activated by applying a minimum of 100 (free running)
TCK pulses to the device after nTRST is pulled high.
It's not clear whether that means TMS high, low, or don't-care.
Does anyone know?
If it's not "TMS low" then I wonder if it's practical to make normal
startup processing -- or entry to JTAG's RESET state -- always do
that. Could it hurt anything?
If "TMS low" works then it's a bit sad that JRCs aren't targets.
Else the reset-deassert-post handler could just "runtest 100";
those handlers don't kick in for TAPs, just targets. (Which
seems like a non-useful restriction, FWIW.)
- Dave
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