DM6467 booting strange behaviour

Sid

Hi All,

A friend of mine, using a custom made board consisting of DM6467, noticed a strange behaviour.

He set the boot mode to UART boot, but couldn't get BOOTME message on hyperterminal.

The settings were 115200n8 (same as those suggested for DM6467 EVM).

He tried using the CRO for debugging, by observing the signals for UART on the board. But he noticed a strange behaviour. When he connected the oscilloscope probe ground to the Ground terminal of the board, he started receiving BOOTME message, but when he disconnected the oscilloscope, the BOOTME message no longer appeared.

I am not sure whether it is some sort of hardware design problem, or grounding problem, or some other problem. I am also confused as to how the connection of an external probe ground could result in such a situation.

Has anybody experienced this before? Can somebody suggest a solution for this?

Thanks and Regards,

Sid

over 15 years ago

0 Juan Gonzales over 15 years ago

TI__Mastermind 37340 points

One suggestion would be to have the custom board schematics checked against the DM6467 EVM schematics (available at http://support.spectrumdigital.com/boards/evmdm6467/revf/ )

0 Sid over 15 years ago in reply to Juan Gonzales

Genius 4530 points

Hi Juan,

Thanks for your reply.

Most of the sections (particularly boot sections and UART section) are similar to the schematic.

The power supply section is different though. And with some additional components being present, there are additional supply voltages being generated.

I would like to ask if DM6467 has any power-up sequence, and if this could affect the booting up, as it is affecting in the manner now.

Thanks and regards,

Sid

0 Juan Gonzales over 15 years ago in reply to Sid

TI__Mastermind 37340 points

power-up sequencing is important on this part; this is described in section 7.3 of the main data-sheet. Violating the power sequence can cause the part to mal-function.

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DM6467 booting strange behaviour