I'm scratching my head with this one... On my custom board, using the Plug-Of-Nails JTAG adapter, it only works from power on if the programmer is attached to the board, but disconnected from the PC. When I apply power, it launches and runs correctly.
If I have the programmer attached to the PC -but not supplying power-, a strobe of the reset line must be performed for the uC to start up.
If I have the programmer attached, the POR executes correctly when I apply power from the programmer.
If I don't have the programmer attached, even strobing the reset does nothing until the programmer is attached.
Main power comes from a 5V regulator, followed by a 3.3V LDO (JTAG & Peripherals) in parallel with a 2.5V LDO (Vcore).
If the programmer is supplying power, the 5V comes from the JTAG interface and runs to the other to regulators.
I have 100k pullups to 3.3V on all my JTAG lines...
Reset was bare to the switch, but I added a 1K pullup - no change.
Anybod have any ideas to help me direct my scope probe?
As an aside, why isn't the reset line run to the JTAG port? I've had some test boards where I created a tight loop and had to use the RST->BMI to regain access to the board; if the RST line went to JTAG, it wouldn't have needed handholding like that.