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Re: motoroladsp] Protecting Flash memory on DSP56F80x devices

Started by David D March 7, 2002
Taking Roelof Oelofsen's suggestion a little further, one could
pin out the JTAG/OnCE connector differently and using a
different connector than what Motorola uses.

Additionally, a 0 Ohm resistor that ties TRST to RESET on your
production boards would prevent a rogue using the debugger
from working unless that person knew where and how the two
lines were connected together. You'd still be able to debug your
board, since the resistor is easily removed/replaced. (The
debugger needs to independently assert RESET and TRST to
be able to control the DSP.)

A generous gob of epoxy over the DSP package (or at least the
JTAG/OnCE pins) would prevent all but the most determined
rogue from getting at your code. (If they have the technology
and desire to remove the epoxy, they very likely have the ability
to microprobe the device to get at the code, even if security were
implemented inside the device...) The rogue would first have to
remove the epoxy to trace back the JTAG/OnCE pins to the
debug connector AND find the short between TRST and RESET
before they could do anything useful with the device. The likelihood
of a first pass success for someone unfamiliar with epoxy removal
is low, so it would very likely take several tries with more than one
of your application boards to yield success.

--david