DP83848K: Input condition of MDC pin during power on or Reset

toshi-e2e

Part Number: DP83848K

Hi all,

Regarding Figure 5-1. Power Up Timing timing diagram,
does the MDC pin need to stay low during T2.1.1 after Power up? Is there any problem even in the High state?

Regarding Figure 5-2 Regarding Reset Timing,
is it necessary to set the MDC to Low during the RESET period (T2.2.4) and T2.2.1? Is there any problem even in the High state?

The background of the question is that the pin connected to the MDC is pulled up when the CPU is powered up, so I want to check if the MDC must be set to Low as shown in the timing diagram when resetting the PHY.

Best regards,
Toshi

over 3 years ago

+1 Kallikuppa Sreenivasa over 3 years ago

TI__Guru*** 146369 points

Hello Toshi,

Thank you for the query.

It is preferred to have the MDC pulled down. it the MDC is pulled up during MCU power up before applying power to the EPHY, this is not recommended.

If the Power is applied and the MDC is pulled high during the startup, please ensure the MDC is not clocking and you make it low before releasing the device reset.

The MDC clock should start only after the power is stabilized.

Regards,

Sreenivasa

0 Tao_2199 over 3 years ago in reply to Kallikuppa Sreenivasa

Genius 5720 points

Hello Sreenivasa,

I have a few questions in addition to Toshi’s question.

(1)　MDC Low before device reset, how long is it needed?

(More than 0 sec?)

(2) T2.2.1 is 3us (typ). How long minimum is needed?

Regards,

Tao_2199

0 Kallikuppa Sreenivasa over 3 years ago in reply to Tao_2199

TI__Guru*** 146369 points

Hello Toshi,

Thank you for the inputs.

Please see below. The timing for power-up and reset is different.

For the reset as shown in the figure, may be you can follow the 3us time for both cases.

Regards,

Sreenivasa

0 Tao_2199 over 3 years ago in reply to Kallikuppa Sreenivasa

Genius 5720 points

Hello Sreenivasa,

Thank you for reply.

I have a question about item (1).

･When performing hard reset after the Vcc and clock are stabled,

it makes RESET_N and MDC low at the same time.

Is this right?

Regards,

Tao_2199

+1 Kallikuppa Sreenivasa over 3 years ago in reply to Tao_2199

TI__Guru*** 146369 points

Hello Toshi,

Thank you for the reply.

Yes, you are right.

Regards.

Sreenivasa

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DP83848K: Input condition of MDC pin during power on or Reset