SN74LVC8T245: SN74LVC8T245RHLR Schematic Review Ethernet MAC TO MAC Communication

HARI T O1

Part Number: SN74LVC8T245
Other Parts Discussed in Thread: TXU0304, TXU0104, TXU0204

Dear Team,

In my board a processor and a microcontroller are communicating using ethernet interface.This is a mac to mac connection.

The processor is working at 3.3V domain and controller at 5V domain.SN74LVC8T245RHLR is used as the level shifter.

May I know my connections are fine or not.I mean the direction selection of SN74LVC8T245RHLR for RX and TX of RMII.

My PIN mapping is given below.

Schematic is given below.

RMII Signal Descriptions of SAMAD52

Regards

HARI

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 317390 points

According to Wikipedia, TXD0, TXD1, and TX_EN go from the MAC to the PHY; RXD0, RXD1, and RX_DV go from the PHY to the MAC, and the clock direction depends on the application.

You have only seven signals. Consider a combination of two TXU0104/TXU0204/TXU0304 chips.

0 HARI T O1 over 2 years ago in reply to Clemens Ladisch

Expert 1665 points

This is a MAC to MAC communication.

May I know the chips you suggested supports the speed of RMII

0 Clemens Ladisch over 2 years ago in reply to HARI T O1

Guru 317390 points

The pin mapping table, the schematic, and the datasheet all use different signal names. But it appears that the direction of the signal at the A2/B2 pins of U16 is wrong.

At these voltages, the TXU devices support at least 125 Mbps.

0 HARI T O1 over 2 years ago in reply to Clemens Ladisch

Expert 1665 points

FOR MAC TO MAC

RMII_MAC_TO_MAC_SAMA5D27_S32K148.pdf

This is the complete schematic.Could you please check

0 Clemens Ladisch over 2 years ago in reply to HARI T O1

Guru 317390 points

As I said, the RMII_GTXEN_SAMA5D2 signals appears to have the wrong direction. (The two TX_EN/RX_DV connections must go in opposite directions.)

I do not know how you have configured the clock.

0 HARI T O1 over 2 years ago in reply to Clemens Ladisch

Expert 1665 points

For RMII there is only one clock

I think I connected the clock in the wrong way clock is coming from my micorocontroller (5V Domain ) then it is going to the SAMA5D2

So clock should be connected to U15.

0 HARI T O1 over 2 years ago in reply to HARI T O1

Expert 1665 points

Hi Clemens,

Thank you for your support.

I am adding the latest schematic.

If you don't mind could you please check.

RMII_MAC TO MAC Review.pdf

Regards

HARI

0 Clemens Ladisch over 2 years ago in reply to HARI T O1

Guru 317390 points

Unused inputs must not be left floating; connect them to GND or V_CC. Otherwise, there are no obvious problems.

+1 HARI T O1 over 2 years ago in reply to Clemens Ladisch

Expert 1665 points

Thank you.

I will connect all A and B pins to GND

Logic

Logic forum

SN74LVC8T245: SN74LVC8T245RHLR Schematic Review Ethernet MAC TO MAC Communication