ETH#03 in TM4C129x Silicon Errata(SPMZ850F)

Yuichiro Kimura

Hello,

For ETH#03 in TM4C129x Silicon Errata(SPMZ850F),
I have a some questions.

1. JTAG may not work
There is a following of a such a description.
Also if a 25MHz crystal is used without RBIAS resistor, then JTAG may not work.
But, there is a following of a such a description in datasheet P.1941.
The internal Ethernet PHY should not be enabled when RBIAS is not connected.
The ROM boot loader will enable the internal Ethernet Phy if no code is present
in the flash and a 24-25Mhz crystal is attached to the OSC0/1 pins.

Regardless of the frequency of the external crystal, if there is no RBIAS resistance,
we understand the JTAG does not work. Is it a Correct?
Selected Crystal values:　24.576MHz(unuse EtherPHY)

2.RBIAS resistor value
As described in the errata, we connected to the 4.7KΩ ± 10% of the resistance
to RBIAS pin.
However, JTAG does not work. why?
What are the safe resistor value?

Potential problems
・Point-to-point construction

Best Regards,
sopatopa

over 9 years ago

0 QJ Wang over 9 years ago

TI__Guru**** 197126 points

Hi Sopatopa,

The correct resistor value is 4.7kohm (10%) if the PHY is not used, and 4.87kohm (10%) if the PHY is used. For the 1st question, I will ask our expert to answer.

Regards,
QJ

0 Amit Ashara over 9 years ago

TI__Guru**** 244400 points

Hello Sopatopa

For point #01 it is correct. JTAG may not work.

Regards
Amit

0 Koichiro Tashiro over 9 years ago in reply to Amit Ashara

TI__Mastermind 22935 points

Hi Amit,

Do you know why the 25MHz information was added in ETH#03 ?
This is misleading.

Thanks and regards,
Koichiro

0 Amit Ashara over 9 years ago in reply to Koichiro Tashiro

TI__Guru**** 244400 points

Hello Koichiro,

The 25MHz information is very specific frequency where the JTAG stops working altogether and was requested on the forum.

Regards
Amit

0 Koichiro Tashiro over 9 years ago in reply to Amit Ashara

TI__Mastermind 22935 points

Hi Amit,

I see. As 25MHz is not only frequency the issue happens, Could you update Errata description to avoid confusion at customers ?

Thanks and regards,
Koichiro

0 Amit Ashara over 9 years ago in reply to Koichiro Tashiro

TI__Guru**** 244400 points

Hello Koichiro,

25MHz is where the issue is most likely to happen (at least on the devices we have seen).

Regards
Amit

0 Koichiro Tashiro over 9 years ago in reply to Amit Ashara

TI__Mastermind 22935 points

Hi Amit,

Even though 25MHz is the frequency where the issue most likely seen, current Errata description is misleading.
Customers easily misunderstand 25MHz is only affected frequency.
(at least my customer did)

You don’t agree ?

Thanks and regards,
Koichiro

0 Amit Ashara over 9 years ago in reply to Koichiro Tashiro

TI__Guru**** 244400 points

Hello Koichiro

The errata statement states that it JTAG may not work at 25MHz, but does not negate that it will work at other frequencies.

Regards
Amit

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ETH#03 in TM4C129x Silicon Errata(SPMZ850F)