NET AIC+ problem

[allanleo 0]

I have a big problem with networking 2 micrologix 1500 and 1 panelview300 (with rs232:DH485 protocol) I have 2 net AIC+ converter connecting the 2 micrologix(connected to port 2),and the 2 NET AIC+ are connected to port 3. I cant seem to find the two micrologix in RSlinx if i connect my laptop to port 1 using AB DF1 protocol. I only see one micrologix ,and it is always displayed node 1 even if my Micrologix is configured as node 4 in the DH485 network. If I want to connect the Panelview, where do i connect it, to port 1 of either the Net AIC+? or to port 3? (I have a PV300 with DH485 comm, but the sticker at the back says rs232) Thanks a lot!!

[Guest PhilipW]

Allen This one is real easy to get confused on ...I'll try not to add to it. The standards called RS-232, RS-422 and RS-485 are electrical standards that define things like, voltage levels, baud rates, connectors and cable lengths. If these rules are followed then the connected devices will be able to send a receive data in an electrical sense, BUT there is NO definition of what the data means. In order to allow the connected devices to make use of the data, they need to share the same protocols that define things like, source and destination, type of data, length of data, whether it is a read or write, and various commands needed for things like error checking. All Allen Bradley processors share a common protocol called DF1 for this purpose. It allows a message to get from one device and succesfully arrive in another and convey some meaning...such as write a new value to a datatable. If you are just connecting one device to another, ie your PC to the Serial Port Ch0 on a MicroLogix, then electrically a RS-232 connection is all that is needed. In RSLinx you add a new "RS_232 DF1" driver and away you go. But if you are connecting more than two devices together the network needs two more features: 1. The electrical standard must be different because RS-232 is only able to handle two devices, point to point. In the network you are using the NET-AIC's are linked together using a version of RS-485 which allows up to 32 devices to exist on the same cable. 2. You also need the another protocol that lets the network of multiple devices work properly. For example, because only one device can tranmist data on a single cable at a time, there needs to be some way of deciding whose turn it is to transmit. (Plus lots of other fucntions needed to make the network initialise, add and subtract stations etc.) This protocol is added on top of the DF1 layer and is called in this case DH-485. So this is the background to what you are doing. The important thing to note is that the electrical standard, and the network layer are not the same thing, and there is no fixed arangement that says DH-485 always runs on RSS485 cable. If for example there are only TWO electrical connections in your network, ie your PC's RS-232 port plugged into the port 2 of the AIC (The AIC is an electrical isolator so there is no electrical connection to any other device on the network), then this will work fine electrically. But you can run on that RS-232 connection either straight DF1 if there is only ONE other device on the other side of the AIC and it is set up for DF1 as well OR (and now we get to the nub of it)...you can ask for a DH-485 protocol to run over the RS-232 connection in order to connect to multiple devices, all set up for DH-485. So in a nutshell if you go back into RSLinx and delete the RS-232 DF1 driver, and add instead a "1747-PIC/AIC+" driver then your PC will run "DH-485" out its serial port and the whole network should burst into life. When setting up the AIC+ driver you will be asked for an Address...normally DH-485 is set up with addresses running from 0, 1, 2, 3.... just make sure each device has a unique address. The PanelView follows the same idea...the electrical port is RS-232 and will connect to an AIC port 2, but the protocol will need to be DH-485. Check the part number and make sure you have the right version. If you have a RS-232 /DF1 PanelView then the comms isn't going to work on a network with multiple devices like this.. Sorry this is a little pedantic...but I hope it helps.

[Guest PhilipW]

I just read your question again...and there is one more thing. The reason why you are seeing one MicroLogix on Node 1, is that the Micro's do a neat trick of autodetecting if the data they are getting is using just DF1 or has a DH-485 layer on top...and automatically reply in the right protocol. The default node address for DF1(Full Duplex) is always 1. (On a point to point network no other addresses have any meaing.) One of the Micro's is answering your RSLinx DF1 driver, but the other isn't getting a look in because DF1(Full Duplex) can only handle one device, ie your PC talking to one other, ie one of the Micro's. This is normally a useful trick because is allows a Micro set up for DH-485 to respond to someone trying to get online with just a direct serial cable using DF1....but in this case it has been a little misleading because it kinda looked like the DF1 driver might work.

[allanleo 0]

Thanks philipW I tried what you said about deleting the RS232-DF1 driver and adding the 1747-PIC/AIC+ driver, whe i did this, i can't see any Micorologix. I used the same cable (--CP3 cable) when i tried to connect again using the DF1 driver, and i see one micrologix. do I need to use another cable when using the AIC+ driver? (see drawing) As for the Panelview300, I have the one with DH485 (with an RS232 db9 port), i made a cable using only the pins 2,3 and 5(without any jumpers for the CTS,RTS,etc) that i connect to the port2 of AIC+, and still it is reporting that there is no node found on the network, the baud settings are correct on the AIC+ and the panelview. Do i have to use a special cable for this? if so can anyone provide me with the pinouts? I tried configuring chanel1 of one of the micrologix to DH485 and connect the panelview to it directly using the cable i made, and it is working.(the panelview can communicate with the micrologix) I'm really out of ideas what to do next. your reply is very much appreciated... allan

[allanleo 0]

Finally I made the DH485 Network work!, I just made a stupid setting for channel 0 of the micrologix plc, i set it to DF1 and not to DH485... thanks again philipW