AM5716: Pullup on TMS and TCLK signals

Patrick Ruf

Part Number: AM5716

Hi,

In the "AM57xx Schematic Checklist" it is written that TMS and TCLK need an external 4k7 pullup resistor to VDDSHV3. In the current datasheet I can see that TMS needs an external pullup but not TCLK (Table 4-28). Also in the AM571x IDK EVM schematic are no external pullups as far as I can see.

Does TCLK pin needs an external 4.7k pullup?

Best regards,
Patrick

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

The factory team have been notified. They will respond here.

0 Tom Johnson 16214 over 7 years ago in reply to Biser Gatchev-XID

TI__Mastermind 46460 points

The AM5716 contains internal pull resistors to keep them at their inert levels. If track is added, these signals should have external pull resistors added for optimum noise immunity. Therefore, TCK, TDI and TMS should have external pull-up resistors and TRSTn should have an external pull-down resistor when an emulator connection is implemented. This is consistent with the general JTAG guidance provided in SPRU655 and related documents.

The AM57xx IDK boards were implemented with multiple configuration options. Unfortunately, these were omitted. They should be present for optimum robustness.

Tom

0 Tom Johnson 16214 over 7 years ago in reply to Tom Johnson 16214

TI__Mastermind 46460 points

The guidance in Table 4-27 is generic - even applicable when no JTAG emulation is attached. The TMS pin does not have any internal pull resistor active when the device is in reset or when exiting reset. It always needs an external pull resistor. The other JTAG input signals do have internal pull resistors active when in reset and when exiting reset.

Tom

0 Patrick Ruf over 7 years ago in reply to Tom Johnson 16214

Genius 4950 points

Tom,

Thanks for this clear answer and the additional information. We will implement all the recommended pullups and pulldowns.

Best regards,
Patrick

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AM5716: Pullup on TMS and TCLK signals