Does the MM300 actually have RS-232c capability? I'm pretty sure it can run RS-485 and Ethernet, and maybe another protocol like Profibus (haven't used it, whatever it is).
You can't persuade the Ethernet port to talk directly to a serial port, that's just not going to happen.
This plus a commercially available RS-232 to RS485 converter should do the trick. I have several of these converters ranging in price from about $15 to maybe $125. You shouldn't have to worry about the pinouts. 2 wire & common into the converter and that connects either to a 9 pin RS-232 or you can get converters that are USB and skip an extra connection.
All of this information is readily available on the GE website. Some would say RTFM. MM300 Communications Guide
Whoa. Check out the wiring terminal diagram in the MM300 manual on page 28.
RS-485 is NOT the RJ45 connector, it's screw terminals.
The MM300 uses RS-485 for Modbus RTU. Either RS-232/RS-485 or USB/RS-485 requires a 'converter' to convert from one electrical standard to the other using active components. It's not just passive cable wiring to make the conversion.
There are commercially available serial RS-232/RS-485 or USB/RS-485 converters. For RS-485 converter, I recommend those using the FTDI chipset. As my Daddy used to say, "Son, there's nothing someone can't make cheaper, but you'll pay the price in the end". If the device doesn't tell you it uses an FTDI chipset, it doesn't. Avoid the alternative.
USB/485 or 232/485 connector can be purchased with screw terminal connections (Some 232/485 use a DB9 on the 232 side).
Comment on GE's MM300 communication manual - it has probably the best description of Modbus implementation I've ever read, and I've read hundreds. Worth the read.
Ok guys, I have read this manual more precise and I have some problems
This is a part of wiring diagram of a motor feeder.
I have a ethernet connector on front plate, so I have only one way to connect to this IED, because of a cubicle is normal in a work position and I don't have access to others connectors. Do I correct understand that this port use RS485? And which cable I should use to connect to this port?
I haven't a clue what your diagram is. I don't have one of these MM300; I have never seen one. I can only go by the diagram from the MM300 manual I found that shows DIN rail mounted modules and RS-485 terminals.
I have on way of reconciling your diagram to the one I found.
The RS232 port is on the side of the unit, uses an RJ45 connector, and is labeled "RS485 to control panel". Yup, doesn't get any more confusing than that.
The GE part number for the RJ45/RS232 "custom cable" is 0804-0180. You may be able to ask GE for the pinout or just go ahead and order one. I don't have one, otherwise I would ring it out and post the pinout for you.
If the task is to use the RS-232 port for firmware updates, JG2828's screen shot above tells the story.
If the task is to use the RS-232 port for Modbus RTU, it would be prudent to confirm that the Modbus port can be actually be configured as the RS-232 port. The quick scan I did mentioned Modbus only on RS-485 and Devicenet on RS-232.
JG2828, thanks! I didn't have possibility to check this IED in "real", so I could use manual only.
I think this is a spesial cable, and I won't able to find the pinout to it. May be it's way which GE try to earn money.
Also I wrote to GE about a pinout, but they didn't answer.
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