On Sunday 20 September 2009, Michel Catudal wrote: > > Nexus sits on top of JTAG.. > > I know that but that doesn't change the fact that it is a different > protocol than the Atmel JTAGII.
For the JTAG signals, it's the same protocol. Same state machine, etc. For the "auxiliary port" it's what Nexus specifies; same kind of difference as with the ARM trace port. ISTR that both are bidirectional parallel interfaces, plus normal JTAG signals. And both use 38-pin Mictor connectors; but the pinouts aren't compatible (no surprise). > The nexus debugger is very expensive while the JTAGII debugger is not > quite as expensive (around $300) "JTAGICE mkII" JTAG-only debugger, vs "AVR ONE!". Both support basic Nexus operations. The mkII periodically gets specials; I saw them last year for $100 including a devel board. The difference is the same as between ARM debuggers that support the trace port and those which only deal with the JTAG signals, except I think the "AVR ONE!" is a bunch cheaper than any product I've seen that supports the ARM ETM trace. ($600 -- price is down! -- vs at least four or five times as much.) There are two key protocols involved. One is the JTAG level stuff, which I understand to be the same. The other is the command protocol over USB. It'd make sense that those differ, minimally because the mkII doesn't support streaming of (voluminous!) trace data. Both also support some non-JTAG protocols. "DebugWire" is a 1-wire variant that's Atmel-private; used on many AVR8 chips, including the 8-pin ATtiny ones. There's a newish "PDI" thing, which I've forgotten about. But there's no reason OpenOCD shouldn't be able to support the Nexus-over-JTAG stuff. It's how AVR32 chips work using the mkII after all. - Dave _______________________________________________ Openocd-development mailing list Openocd-development@lists.berlios.de https://lists.berlios.de/mailman/listinfo/openocd-development
