XVME-661 Reflection memory card
Real-time communication network is a special network communication technology for applications requiring high real-time requirements, which is generally realized by shared memory technology based on high-speed network. In addition to the strict transmission certainty and predictability, it also has the characteristics of high speed, simple communication protocol, light host load, strong adaptability of hardware and software platforms, reliable transmission error correction ability, support for interrupt signal transmission and so on
In this scheme, XVME-661 GE FANUC’s reflection memory card is used to construct a real-time reflection memory network. In addition to the advantages of common shared memory networks, the real-time network also has the advantages of small network delay, mature technology, high reliability, simple integration and easy expansion
The reflection memory card connection is divided into two kinds: one-way ring connection and star connection. The one-way ring network structure has the inherent “no conflict”, “full load”, natural ordering and strict determination of transmission delay. Under this network structure, no matter how all nodes burst or continue to transmit data at the maximum rate at the same time, the ring network can naturally achieve conflict-free sorting and propagation with the help of the physical structure, without any adverse impact on the real-time performance of the network and transmission performance. Once the network is formed, the transmission delay between any two points is strictly determined. Not only that, the data sender can also use the ring loop, real-time reliable calculation of transmission delay and receive confirmation, with extremely high fault tolerance and reliability. However, the one-way ring connection method has a disadvantage, that is, all the boards must be powered up before they can work. The way to solve this problem is to use a star connection, by reflecting the memory HUB to bypass the damaged or power down board, forming a more stable network structure
XVME-661 Reflected memory is a strong real-time high-bandwidth LAN technology that provides efficient data transfer between interconnected computers. This technology has been widely used in the field of strong real-time network applications
A reflective memory network virtualizes a globally shared network memory across all interconnected nodes, enabling memory-to-memory communication in a distributed system, so there is no software overhead for applications.XVME-661 Each node machine is inserted with a reflective memory card with dual-port memory. The application software of each node can directly read and write the memory on the reflected memory card. When data is written to the memory of a reflective memory card in one machine, the reflective memory card is automatically transmitted via optical fibers to the corresponding location in the memory of all other reflective memory cards connected to the network, with a transmission delay of only a few hundred nanoseconds. That is, the memory on all reflective memory cards is always updated synchronously to the exact same content, as if a piece of global shared memory were virtual. When each node machine accesses data, it only needs to access the local reflected memory card memory, without device drivers and network protocols
Reflective memory networks have the following main features
XVME-661 High speed and performance
XVME-661 Because reflected memory network can greatly improve the communication speed between cluster systems, it is especially suitable for replacing the traditional LANs, bus transponder and DMA can not meet the needs of applications. The latest GE FUNAC 5565 Series reflective memory card has a transfer speed of 174M bytes per second. Using optical fiber, it can not only connect more nodes (up to 256 nodes), but also has high impact resistance and anti-interference performance. Reflective memory cards are completely physical communications that do not require any software protocol overhead, which is unmatched by other LAN transmissions. The test results show that there is a delay of less than 400 nanoseconds from the time data is written to RAM to the reflected memory card at another node