DRA75: Are external PullUp/Down resistors always needed for TMS(F18), TRST(D20) and TCLK(E20) pins?

Shinsuke Tanaka

Part Number: DRA75

Dear Sirs or Madams,

According to Table 4-1 shown on DRA75x datasheet revised NOVEMBER 2018,

TMS(F18), TRST(D20) and TCLK(E20) pins require external PullUp/Down resistors "when unused".

Considering that these pins are related to JTAG function and they can be considered as "unused" when JTAG device is NOT connected to DRA75 externally,

we now understand that external PullUp/Down resistors have to be connected to these pins regardless whether JTAG function of DRA75 is used or NOT.

Is our above understanding cprrect?

Best regards,

Shinsuke Tanaka

over 6 years ago

0 Stanislav Stilyanov over 6 years ago

TI__Mastermind 18400 points

Hello Tanaka-san,

I guess they wanted to say "when JTAG is unused in the design and connector isn't implemented, these pins require weak pullups/pulldowns"
Otherwise, when JTAG connector is present, strong (2.2-4.7k) pullups/pulldowns are required as per JTAG standard as usual.

Regards,
Stan

0 Shinsuke Tanaka over 6 years ago in reply to Stanislav Stilyanov

Intellectual 520 points

Dear Mr.Stilyanov,

I appreciate your rapid response.

>Otherwise, when JTAG connector is present, strong (2.2-4.7k) pullups/pulldowns are required
>as per JTAG standard as usual.
Please let me have one more question to deepen my understandings.
Do you mean that (2.2-4.7k) pullups/pulldowns should always be connected to
TMS(F18), TRST(D20) and TCLK(E20) pins on the PCB as long as a JTAG connector exists on the PCB?

Best regards,
Shinsuke Tanaka

0 Stanislav Stilyanov over 6 years ago in reply to Shinsuke Tanaka

TI__Mastermind 18400 points

Yes, that's correct.
I'm not familiar enough with JTAG but these pull resistors I can find on EVM:

TMS - 4.7k pullup to 3.3V
TRSTn - 4.7k pulldown to GND
TCLK - can't find pull

0 Stanislav Stilyanov over 6 years ago in reply to Stanislav Stilyanov

TI__Mastermind 18400 points

TCLK - 4.7k pullup

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DRA75: Are external PullUp/Down resistors always needed for TMS(F18), TRST(D20) and TCLK(E20) pins?