CC2538 unused JTAG pins

Dan O'Connell

Genius 3135 points

Other Parts Discussed in Thread: CC2538

Hi,

We are busy with our final PCB design with a CC2538.

What does one do with the JTAG pins that are not used? (In particular, JTAG_TMS (pin 46) and JTAG_TCK (pin 47). )

Where does one find this info in the User's Guide or datasheet? I did a brief search and could not find anything.

Thanks!

over 11 years ago

0 Suyash Jain over 11 years ago

TI__Genius 10650 points

Generally it is recommended to set unused GPIO pins as input with pullups. On CC2538 this is the default state after power up for the GPIO's. Also, you can decide to connect these pins to a test port in case your application requires it in future or you need it for some other purposes.

0 Armandt van Rooyen over 11 years ago in reply to Suyash Jain

Prodigy 50 points

Suyash...

Read the question, they are NOT GPIO pins, provide a better answer.

0 Armandt van Rooyen over 11 years ago in reply to Armandt van Rooyen

Prodigy 50 points

Suyash,

We are using the CC2538DK. In our prototype design we are using the CC2538EM as a daughter board. Currently we are using the SmartRF06 to program the CC2538EM which gets plugged onto our prototype.

Since there are currently no programming circuitry on the prototype board, JTAG_TCK and JTAG_TMS are not used. These two pins are on the EM connectors of the CC2538EM.

Since JTAG operation should probably be universal, I found some sources which indicates what to do when these two pins are unused.

ARM

ALTERA

These sources indicate that TMS requires a pull-up and TCK requires a pull-down. I also measured the pins of the EM connectors on the SmartRF06 board in non-programming mode and the TMS and TCK pins were high and low, respectively.

Of course nothing in the world is ever always the same so here I ask for confirmation. What do you think?

0 TIABO over 11 years ago in reply to Armandt van Rooyen

TI__Genius 12900 points

This should be true for CC2538 as well.

Br,
TIABO

0 TA12012 over 11 years ago in reply to Armandt van Rooyen

TI__Mastermind 36395 points

Armandt,

Please, there is no need to be rude on this forum.

The user guide actually contains the information you are looking for but it is pretty hard to find. So I will include a screen capture from the online PDF.

TDI and TDO are general purpose IOs when JTAG is not used, so internal default IO config apply. However the TMS and TCK are dedicated JTAG pins are documented on table 6.1 in the UG. TMS is input pull-up and TCK is input pull-down see below.

This is aligned with what Altera and ARM says on the links provided too.

/TA

0 Armandt van Rooyen over 11 years ago in reply to TA12012

Prodigy 50 points

TA,

My apologies for being so blunt and coming across rude.

Thank you for your wonderful answer and source.

Armandt

0 Dan O'Connell over 11 years ago in reply to TA12012

Genius 3135 points

Great, thanks for everyone's input.

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CC2538 unused JTAG pins