DP83869HM: JTAG

kathy jacques

Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

I am trying to scan the JTAG chain and verify that this device shows up correctly in the chain. It looks like the TDO signal is never toggling.

I have verified CLK/TMS/TDI and they look good.

The datasheet indicates that to reset the JTAG it needs 3 clock cycles with TMS high. I see about 6 clock cycles with TMS high.

I have tried with the strapping bits set for: JTAG Boundary scan and RGMII to 1000Base-X, with no difference.

Is there something else that needs to be done to make this work?

over 2 years ago

0 Kallikuppa Sreenivasa over 2 years ago

TI__Guru** 124028 points

Hello Kathy,

Thank you for checking.

Can you provide some additional details on how you are performing the tests. and the BSDL file you are using.

Regards,

Seenivasa

0 kathy jacques over 2 years ago in reply to Kallikuppa Sreenivasa

Prodigy 20 points

I am not using a BSDL file. I am using a Microsemi (Microchip) FlashPro 5 programming pod to just scan the chain and verify all of my devices answer up with their device ID. I am just trying to verify the integrity of the scan chain.

If I jumper around the TI PHY devices in my chain, everything answers up correctly.

With the TI PHYs in the chain, I see no activity on the TDO signal of the TI PHY.

I am trying to understand the following:

1. should this work?

2. is there something that i am doing wrong?

0 Kallikuppa Sreenivasa over 2 years ago in reply to kathy jacques

TI__Guru** 124028 points

Hello Kathy,

Thank you for the note. Do you have a block diagram with a couple of device names in the chain other than he TI devices for me to check.

Regards,

Sreenivasa

0 kathy jacques over 2 years ago in reply to Kallikuppa Sreenivasa

Prodigy 20 points

One of the other devices is Broadcom PEX8780 PCIe switch.

0 Kallikuppa Sreenivasa over 2 years ago in reply to kathy jacques

TI__Guru** 124028 points

Hello Kathy,

Thank you. If i understand correctly, you have multiple devices connected in the JTAG chain.

Can you please check the IO voltage comparability between devices.

Regards,

Sreenivasa

0 kathy jacques over 2 years ago in reply to Kallikuppa Sreenivasa

Prodigy 20 points

VDDIO of the device is connected to 1.8V. All JTAG signals going to the device are 1.8V.

0 Kallikuppa Sreenivasa over 2 years ago in reply to kathy jacques

TI__Guru** 124028 points

Hello Kathy,

Thank you for the input. Are all device in the network running on 1.8V IO ?

If you check only the PHY, can you read it.

Regard,

Sreenivasa

0 Kallikuppa Sreenivasa over 2 years ago in reply to Kallikuppa Sreenivasa

TI__Guru** 124028 points

Hello Kathy,

Do you have some inputs.

Regards,

Sreenivasa

0 kathy jacques over 2 years ago in reply to Kallikuppa Sreenivasa

Prodigy 20 points

I don't have an easy way to put only the TI PHY in the chain. The device preceeding the PHY in the chain is 1.8V, but the previous devices are all a higher voltage. The device preceeding it in the chain seems to be discovered correctly (if I jumper around the PHYs, the chain discovers all devices).

Is there mode that would cause the TDO to not operate? I always see TDO as low.

Do I need to use the strapping bits to tell the chip to be in boundary scan mode? It doesn't seem to change the behavior of TDO if I set the straps for 111 (JTAG for boundary scan) or 001 (RGMII to 1000Base-X)

0 Kallikuppa Sreenivasa over 2 years ago in reply to kathy jacques

TI__Guru** 124028 points

Hello Kathy,

Thank you for the inputs. Do you have a diagram that i could review.

With the IO being 1.8V, the TDI voltage seems to 3.3V if my understanding is correct. Is there a way to scale this voltage to 1.8V. How about termination of other JTAG signals.

Regards,

Sreenivasa

0 kathy jacques over 2 years ago in reply to Kallikuppa Sreenivasa

Prodigy 20 points

Each device in the chain has a dedicated TCK signal, to avoid any SI issues with the clock.

TMS is shared between the two TI PHYs and the Broadcom PEX8780, which is directly before the PHYs in the chain, and also uses 1.8V signaling.

The TDI to the first TI PHY is from the Broadcom PEX8780 and is a direct connection. This signal looks as expected with the ID's of the various devices in the chain, plus the 'signature' from the Flash Pro that get appended to the end of the chain.

The TDO from each TI PHY have a 2.5K pull-up to 1.8V. Since this signal is always low, the PHY must be driving it low.

0 Kallikuppa Sreenivasa over 2 years ago in reply to kathy jacques

TI__Guru** 124028 points

Hello Kathy,

Thank you for the reply and explanation.

Do you have an option to increase the vddio of the dp83869 to 3.3V for a quick test ?

You mentioned there are 2 X DP83869. Do you see a way to check only these 2 devices in the chain.

Regards,

Sreenivasa

0 kathy jacques over 2 years ago in reply to Kallikuppa Sreenivasa

Prodigy 20 points

It would not be easy to change to 3.3V. I will investigate to see if there is a way, but it might take a bit of work.

I could put the two PHYs as the only devices in the chain if i feed the TDI with a 3.3V signal, but that doesn't seem like a great idea.

Are there any other input signals that might either disable the JTAG, or put the TDO pin in a different mode? I'm sure that reset is deasserted, but I wasn't sure if any other pins might be interesting/important...

0 Kallikuppa Sreenivasa over 2 years ago in reply to kathy jacques

TI__Guru** 124028 points

Hello Kathy,

Thank you for the input.

It would not be easy to change to 3.3V. I will investigate to see if there is a way, but it might take a bit of work.

Noted and let me know what you observe

Let me check on this.

Regards,

Sreenivasa

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DP83869HM: JTAG