RM48 - Pull up on TCK

R11

Other Parts Discussed in Thread: RM48L950

The RM48 HDK schematic shows R126, R127, and R128 as pull-ups on the JTAG port of the RM48. According to Table 2-19 of the RM48L950 datasheet, the pull-up on TCK is opposite to the default pull-type internal to the MCU for that pin (default pull-type is down for TCK). What is the reason for pulling up TCK externally? I have seen external resistors used on JTAG signal before, but have always seen them used for additional pull in the same direction as the processor default, never against the default pull.

over 12 years ago

0 Wen-Shin Wang over 12 years ago

TI__Genius 14070 points

Hello Rustin,

The Hercules Safety Microcontroller would be the best place to help answer this question, and I will move this post over.

Hello Team,

Can you please help with Rustin's question above?

Thanks and Best Regards,

Wen-Shin Wang

0 Sunil Oak over 12 years ago

TI__Mastermind 49120 points

Rustin,

That's a good catch. The RM48x MCUs are designed with an internal pull-down on TCK. So the external circuit needs to either also pull TCK down or leave the pull resistor off.

Regards, Sunil

0 Jason Zhang over 10 years ago in reply to Sunil Oak

TI__Expert 3690 points

Hi Sunil, One of our customers just asked me the same question today as you discussed. Because in our EVM, the pull-up resistor is used. Also most of our customers also added the pull-up resistor on TCK pin. It seems the JTAG circuit also works well even we added this resister. Do you have any suggestion on it? Should customer remove this pull-up resistor? Thanks!

0 Sunil Oak over 10 years ago in reply to Jason Zhang

TI__Mastermind 49120 points

Generally TCK is required to have a pull-down. This is what I have seen specified in many emulator datasheets. You need to check if your specific emulator calls for a pull-up. If so, you need to override the internal 20uA pull-down on this pin.

0 Jason Zhang over 10 years ago in reply to Sunil Oak

TI__Expert 3690 points

Hi Sunil,

Got it and thanks!

0 LeonardEllis over 9 years ago in reply to Wen-Shin Wang

TI__Guru 71526 points

Wen-Shin,

One of our customers is designing a mating board for the SAFETI-HSK-RM48 and asked for the CAD or Gerber files. I sent him the link on the RM48_CNCD wiki: http://processors.wiki.ti.com/index.php/RM48_CNCD for the gerbers: RM48_CNCD_Gerbers.zip , but these are not including the HSK board. I cannot find a corresponding wiki or webpage for the HSK, can you please provide, or send the link to me?

Thanks,

~Leonard

0 Anthony F. Seely over 9 years ago in reply to LeonardEllis

TI__Guru 68990 points

Leonard,

It was on a DVD image that was downloadable from Hitex - I can't find a link to that DVD image today though.

There are no signals on the edge connector of the HSK - so it's got the form factor of a control card but it can't actually control anything.
It's meant as a way to quickly demonstrate and benchmark the functions of the safety library rather than being used as a control card.

0 LeonardEllis over 9 years ago in reply to Anthony F. Seely

TI__Guru 71526 points

so you're saying, unlike the CNCD card, the HSK card design files are not available? I believe this customer was going to use this as the basis for their design, not just interface to it.

0 Anthony F. Seely over 9 years ago in reply to LeonardEllis

TI__Guru 68990 points

No, it was available online but I can't find it at the moment. I think the website may have gotten refreshed and the download moved to where I can't find it to point you to it or pulled down. The link on our .ti.com tool folder used to take you to a page with the kit and on that page there was a link to download the updated DVD image --- but that's not working today. I'm working w. our marketing engineer on figuring this out as we speak.

That much said this particular kit has many features for injecting faults that you would not want to include in a design of your own.
It's got a whole separate processor & emulator to act as a fault injector. This would get stripped out if you do your own design.

It is probably better actually to look at the CNCD as a starting point for a design..

0 LeonardEllis over 9 years ago in reply to Anthony F. Seely

TI__Guru 71526 points

What they want is to add SDRAM and Ethernet to the existing HSK board to begin software development. Is this possible with the existing HSK board? After they do the initial development and testing, then they will move to a new pcb design, but first, the concept has to be validated, so adding the SDRAM and HSI is the quickest way to get there.

0 Anthony F. Seely over 9 years ago in reply to LeonardEllis

TI__Guru 68990 points

Leonard,

No EMIF on that board is not even routed.
The only connector is the edge. It's not 100% empty but only 5 pwms, 3 adc, and 2 gio are available on this edge connector. rest are NC.

0 LeonardEllis over 9 years ago in reply to Anthony F. Seely

TI__Guru 71526 points

given what they want to do, what would you recommend?

0 Anthony F. Seely over 9 years ago in reply to LeonardEllis

TI__Guru 68990 points

The only kit we have with SDRAM is the HDK.
It does not have the ability to inject faults like the HSK.

They would need to work on different parts of the project with both kits in parallel, or
try to delay using the SDRAM, until their own hardware becomes available.

Or they could take the design files of the HSK and add an SDRAM as a prototype step, but the HSK
design files are not the simplest because of the dual CPUs and onboard debuggers.

0 Anthony F. Seely over 9 years ago in reply to Anthony F. Seely

TI__Guru 68990 points

e2e.ti.com/.../1809570
posted pdf's there.

0 ?? ? over 9 years ago

Prodigy 40 points

BASE ON THE jtag STANDARD, THE TCK need to pull down.

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RM48 - Pull up on TCK