DP83848J: About LED Behavior issue

yimin bai34

Genius 4755 points

Part Number: DP83848J

Hi Sir

We used DP83848J for development and below is the schematic

we found the behavior of LED_Speed is different.

1. after system power-on without connecting cable, the LED_Speed is on.

2.after finishing system bootup, the LED_Speed is off. we measured this pin is High(3.3V)

Based on the spec's description, LED_Speed is off. -> the PHY's status is 10Mb/s

Q1. we measured RX_CLK and TX_CLK, they are 25Mhz. Based on spec's definition, it should be 100Mb/s in 25MHz of TX_CLK/RX_CLK ?

Q2 we had some boards below above procedures, but LED_Speed is on. we measured this pin is 1.375V(low)

below is the register comparison table. the difference is register 0x10

LED_ON

LED_OFF

Please advise

Yimin

over 6 years ago

0 Geet Modi over 6 years ago

TI__Mastermind 26320 points

Hi Yimin,

I looked at register dumps for both cases. Register 10, indicates both Phy has link in 100M, Full Duplex.

To isolate any assembly level issue, I suggest to try swapping the IC between the two boards and observer the behaviour. Share the register dumps as well.

Regards,
Geet

0 yimin bai34 over 6 years ago in reply to Geet Modi

Genius 4755 points

Hi SIr

thanks for your help. we found the difference is bit 6 Remote Fault.

Could you explain this function in more detailed ? does it cause the the LED behavior difference ?

thanks for your reply.

Yimin

0 Geet Modi over 6 years ago in reply to yimin bai34

TI__Mastermind 26320 points

Remote fault indicates that Link Partner is observing fault on it's Rx which esstentially is Tx of the DUT.

Regards,
Geet

Interface

Interface forum

DP83848J: About LED Behavior issue