The EZ-kit has a pull down resistor on the TRST pin, EE-68 has it
removed and the datasheet says pull it down if NOT used. My customer is
planning to use the connector for both emulation and JTAG testing.
I would sure like to know why EE-68 remove the resistor?
The recommendation for the BF537 is that the design will work with or without a
pulldown resistor applied to the ~TRST signal. This is due to the fact that the
BF537 actually has a weak internal pulldown resistor on this signal (though I
could not find this documented anywhere). If the customer wishes to exercise
prudence, they can apply their own external pulldown that is as strong but no
stronger than the one on the EZ-Kit. They will also be fine without an external
pulldown in their system.
EE-68 discusses JTAG guidelines on a processor by processor basis and this
explains why certain information varies from one processor to the next.
So in this case, we can advise the customer to use their own discretion as the
design will work with or without an external pulldown.