NI FBUS - HSE/H1 Capabilities

Question

I am in the process of looking for alternatives to Rockwell 1757-FFLD (foundation fieldbus linking device).  We have a couple of major issues with this device that are requiring us to look for a different solution.  
1.  Can we use the NI FBUS - HSE/H1 with ControlLogix?  How is this done?
2.  Can the Emerson 375 Fieldbus Communicator communicate on an H1 segment at the same time the NI FBUS - HSE/H1 and does it interrupt communications to the devices on the segment?  The 1757-FFLD does not support this.
3.  Can we add devices and configure to an existing segment with out interrupting the communications to the existing devices.  Explain how the schedule and configuration gets downloaded.  Currently with the 1757-FFLD, when we download the H1 segment we lose communications to all the devices.  As the configuration gets loaded to each device, the device returns online.  We are seeing communication interruptions of 10 minutes because it takes 10 minutes to download that segment.   We could live with a scenario where it momentarily interrupted the communications to 1 specific transmitter while it was downloading to that device.  When we try adding a device online and just download the configuration for the new device, we get a Schedule Download error.  The only way to get a clean download is to download the entire H1 segment. 
4.  What is the recommended number of devices on a segment? 
If you would like to discuss this via phone, I can be reached at 815-774-5278.
Thank you for your time.
Regards,
David Chasse

Answer 1

1. NI FUBUS - HSE/H1 LD will not work with ControlLogix
2. If you have the latest firmware in your 1757-FFLD(C), it fully supports the 375 HHT.
3. You can use NI FBUS Config with 1757-FFLD, however, NI FBUS  Config software does not  allow partial downloads (software imposed limitation)... full downloads stop everything on the segment.  If you are using RSFieldbus software, you can do partial downloads, add IO (FF Scheduled Communicaitons) on the fly w/o disrupting the network. 
4. In theory you can put 31 devices per segment (w/o repeaters), however, this is not practical for various reason (voltage drop, slower updates, VCR connections, and etc.).  The biggest thing to watch is the number of VCRs (producer/consumer connections on H1 are called VCRs).  A valve could produce Postion, Torque, Alarms, DI and then consume CmdPosition... This valve would produce 6 VCRs and consume 1 VCR.  A Temperature probe might only produce one VCR.  The general rule is one or two valves and 6 to 8 other devices per segment.  If you have two valves (2 x 7 VCRs) and four mass flow meters (4 x 5 VCRs) that means you need to move at least 34 packets (one-way) across the network.  FF can only perform 50 messages per second.   The bandwith is split between scheduled and unschedule at about 50/50 ratio so you really only get 25 MGS per second scheduled so you are looking at 1.3 seconds of wire time.   Realize the device require some time to create this data (D/A) before they can publish the data to the network (not less than 50ms, some times as much as 1000ms).  So the real update time could easily be 2 seconds or more (one way across the wire).  Given this performance concern, the original FFLD firmware only supported 16 Producer and 16 Consumer connections (VCRs) per segment...  Many applications consumed many more data points than they produced (especially application that just monitor data and don't do any loops).  So new firmware opens this up to 64 Producer and 64 Consumers per segment..... with a warning that moving this much data across the H1 could be slow.