Cable OFF bit - When does it occur?

TCP/IP Chip W6100
1

Hello,

i am wondering in which cases the “Cable OFF bit” will be set?

(I am using my own PCB-Desing, but with your reference design.)

When i unplug the cable on the W6100s side, PHY-Status is 0x06 - so i know, i have a least no LINK. But i will never get the “Cable OFF bit” set.

When i unplug the cable on the switches’ side only, PHY-Status is 0x86 - so i know, no LINK and “Cable OFF bit” is set.

What is the “Cable OFF bit” intended to detect (in detail)? :slight_smile:

Regards

2

Look here, it says

@details @ref PHYSR_CAB_OFF indicates the cable is off the Ethernet PHY.

@details @ref PHYSR_CAB_OFF indicates the cable is on the Ethernet PHY.

Looks like this bit is about the connection between chip and transformer in standard RJ-45 configuration. This may be useful in direct connection in transformerless configuration. I suspect in this configuration chip can even see connectivity on the TX lines.

The only way to test this hypothesis is to disconnect chip and transformer or jack (if jack has internal transformer).

3

If so, wiznet would have named the bit “Transformer OFF” and not “CABLE OFF”, wouldn’t they?

I am (the chip) able of sensing the cable disconnected:

My design is made after reference design, which all include a transformer. (You don’t want to design without a transformer today, because customers would scream you to hell, because of all your network chips getting destroyed in a rough environment.)

4

Probably yes, bear in mind that WIZnet is Korean company, and it just can be Korean → English translation issue. Not only transformer can be connected to TX/RX lines, thus naming “transformer off” is also incorrect.