ECX - EtherConnect Xtended - High Efficiency Fieldbus and
Reflective Memory Cluster Connect
Reflective Memory Cluster Connect
ECX is a daisy chained Ethernet loop network for connecting real time devices. It offers a number of
significant advantages over regular Ethernet.
- Efficiency – 120 Mbytes/sec sustained user data from one Gb Ethernet link. Topology insures
no collision. - Fixed delay - Flow through packet processing means low and fixed delay.
- Multicast capability – All controllers see every packet. Inherent Multicast.
- Easy cabling, installation – Daisy chain network. No routing table to configure.
- Low Cost – Standard Gb Ethernet components. No Switches required.
- Simplified programming – Easy scheduling, no precise timing.
No Drivers needed. Just Ethernet packets.
- Scalable – Add as many loops as server can handle.
Packets goes from the server to the chain of ECX controllers. Each packet is always forwarded to the
next controller until it reaches the end of the loop. The last controller returns the packet until it
reaches the server. The controllers never generate packets on their own nor consume packets. The
total number of packets sent = the number of packets received.
The server essentially sends out a packet bus to pick up the data at each node. The server has total
control over the timing and source of all data.
Since the packets travel in a fixed sequential path, there is no possibility of collision or congestion.
This topology offers the benefits of immediate feedback when a packet returns and intrinsic flow
control, thus TCP protocol is not needed.
The ECX Network Controller uses flow through or pipelined MACs. A block diagram is shown above.
Each ECX node has 2 MACs, left & right, connected to 2 PHYs & RJ45 jacks.
All of the modules in the above diagram are in one FPGA.
The advantages of the ECX network are:
1. No switches are needed. The chain of ECX controllers are daisy chained and connected directly to
the application server. No switches also mean no routing tables to configure or maintain. The
packets are standard Ethernet packets.
2. Simple cabling. Just connect each ECX to the next. Quick installation.
3. Small FPGA. The ECX controller will fit in the smallest Xilinx Spartan 3 FPGA. Package can be 100
or 144 QFP. Depending on volume, these smallest Xilinx FPGAs can be less than $10.
These FPGAs also come in automotive & mil grade so an ECX design is suitable for harsh
enviroment operation.
4. No external memory chips are needed. FPGA provide memory + registers.
5. Easy shared memory interface with your DSP or SPI interface or any other interface you need.
Very simple programming/control model.
6. No TCP/IP protocol stack needed since flow control is intrinsic and feedback immediate for each
packet sent. Quick error detection and error isolation. The server application controls when a
packet is sent and knows what data should be coming back.
The server side application also does not need multi-threaded protocol stack handling. Packets are
intrinsically sequential so the server packet processing can be simple also. Just a sequential loop.
Less programming effort.
8. High sustained packet rate. With Gb Ethernet, 120MBytes/sec of sustained data bandwidth can
be achieved with a packet size of 650 bytes.
9. The HW requirement for an ECX controller is just a FPGA + 2 PHYs/RJ45. So the HW is the same
as a 2 Ethernet port board. An ECX board can work stand alone or with other boards.
10. ECX is ideal as a backbone for Reflective Memory cluster interconnect.
There are many, many possibilities with ECX. Please inquire.
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