Control logix Ethernet/IP Module

[Jeev]

To that point, I was commissioning some new managed switches today, and the 'crossover' feature, is, by default, disabled. What a surprise.

Sorry to hi-jack the thread, but is there any specific benefit to having that feature disabled? I don't understand why this would even be an option.

 

[ceilingwalker]

The program may or may not be saved on the SD card. The user has to go online and perform a Store procedure using RSLogix 5000 in order to save a binary image of the program and firmware to the SD card.

This image file is NOT readable with desktop software. It can only be read by a controller.

Because the SD card is also an ordinary memory card, I frequently also put a copy of the *.ACD project file from RSLogix 5000 onto the card before I leave a site. But that's not automatic, and I wouldn't count on it having been done by whomever commissioned this system.

It doesn't matter whether you use a DF1 or Ethernet driver in RSLinx Classic to give RSLogix 5000 access to the controller. You still need to do the basic connect and upload steps.

I think some confusion came when the web server feature was mentioned. This is purely a status and informational view of the 1756-ENBT and the controller backplane, and is not a configuration or upload/download tool.

Yes Sir, I misunderstood that. I am having trouble going online with the processor through the EtherNet-IP module. To make matters worse, I have a serial cable that someone has removed the sticker from. It definitely looks AB but which one it is, I have no idea.

 

[Handcraftedsince87]

I could be wrong (it's happened once or twice) but it doesn't have to be an AB serial cable. Any 9 pin D rs232 cable should work for a control logix processor in a rack like you have. I've soldered my own before and we build cables to go from a 9 pin female to a rj45 jack for serial communication between our modem nest and serial to Ethernet conversion modules. There's nothing proprietary about a rs232 cable that I'm aware of besides the ones that go from a standard 9 pin to the small round connector. And I believe that's only on the smaller micrologix controllers

 

[dlweber]

for the SLC it was a null modem cable (pins 2 and 3 crossed) I do not know about control logix if it is a straight through or null modem. For serial that can make a big difference, I do not know of any self detecting crossover in serial technology (like it was mentioned before most modern Ethernet ports are self detecting crossover)

There are some very interesting rs232 cable pinouts out there, AB happens not to be one of them. For instance the Red Lion 4" Kadet...if it is a brand you never used before I would always check the pin outs before trying to connect

 

[Handcraftedsince87]

The one I built for the SLC had pins 2 & 3 crossed.. I thought this was "standard" on a serial cable as I believe I've used the same cable on a control logix processor as well... Good to know about other brands. It looks like a null cable (pins 2 & 3 crossed) is for communication between a processor and computer, and will work for either SLC or Control logix, but if you want to communicate between a cpu and an operator interface like a panelview, it would be a straight through cable. Also good to know, as I've only ever used ethernet

 

[dlweber]

Ethernet is subject to the same kind of thing crossover (equivalent of null modem) cable or straight through, just most modern Ethernet equipment will auto detect which configuration it needs to be in for that cable you have plugged in and compensate for it without any user intervention.

If RS232 would have been a common consumer service it probably would have developed the same technology, but since the general public has basically little to no contact with it (other than old school printers, then people just used the cable that was supplied) it wasn't worth the development money.

 

[Handcraftedsince87]

Sorry to hi-jack the thread, but is there any specific benefit to having that feature disabled? I don't understand why this would even be an option.

I would also like to know

 

[jdbrandt]

I would also like to know

Ask Hirschmann.

They disable it on the RSB020 by default.

 

[ceilingwalker]

I would also like to know

Yes Sir, me to. Please, hi-jack away.

 

[Jeev]

From Wiki (Of course):

Auto MDI-X was developed by Hewlett-Packard engineers Daniel Joseph Dove and Bruce W. Melvin.[2] A pseudo-random number generator decides whether or not a network port will attach its transmitter, or its receiver to each of the twisted pairs used to auto-negotiate the link.[3][4]

When two auto MDI-X ports are connected together, which is normal for modern products, the algorithm resolution time is typically < 500 ms. However, a ~1.4 second asynchronous timer is used to resolve the extremely rare case (with a probability of less than 1 in 5×1021) of a loop where each end keeps switching.[5]

And SuperUser:

However, there are particular devices that do not follow the IEEE 802.3 Auto-Negotiation Protocol, and are instead forced into either 10 Mbps or 100 Mbps operation. Customers who use the Auto-MDI/MDIX algorithm have grown used to not requiring special crossover cables with products that implement the algorithm. When they force speed/duplex for some limited applications, the algorithm breaks down and link is not established. The root of the problem lies in the Auto-Negotiation state machine which turns off an auto-negotiating (AN) transmitter if it detects non-FLP (non Fast Link Pulse) energy on the wire (as occurring during forced mode). When that AN transmitter is turned off, it will cause the Auto-MDI/MDIX node to incorrectly determine its link state and cycle endlessly. The logical elements described below will allow operation of Auto-MDI/MDIX with nodes that are Auto-Negotiating even when the node in question is operated in forced mode.

So I would conclude the answer is:
1) Auto-MDI/X takes longer to establish a connection, which would impact network healing time.
2) Apparently it doesn't work when you explicitly define the speed and duplex.

And that folks, is my TIL!