256MB Reflective Memory Card Single-Mode Fiber

Reflective memory is a technology that provides efficient data transmission between interconnected computers through a local area network, increasingly adopted by designers of strong real-time networks. The concept of reflective memory real-time LAN is quite simple: it involves designing a network memory board that enables memory-to-memory communication in distributed systems without software overhead. Each computer is equipped with a reflective memory card, which features dual-port memory accessible for both reading and writing by various software layers. When data is written into the memory of one machine's reflective memory card, the card automatically transmits it via optical fiber to the memories of other reflective memory cards connected to the network. Typically, within just a few hundred nanoseconds of delay, all reflective memory cards will have the same content written into their memories. Each member can access the data simply by accessing the local reflective memory card's memory. VMIC reflective memory boasts the following key features:

(1) High Speed and Performance

Transmission speeds reach 174 MB/s. Using optical fiber allows connection of more nodes (up to 256 nodes) with strong anti-interference capabilities. Test results show that the delay from data being written into RAM to its transmission to another node's reflective memory card is less than 400 nanoseconds.

(2) Ease of Use

The reflective memory card enables each node to concurrently access the same content by providing an identical data backup to every node machine, making access to the reflective memory card's memory indistinguishable from accessing its own memory. Data consistency among nodes is guaranteed by the reflective memory card and is transparent to application software. Installation is straightforward: simply insert the reflective memory card into an available slot on the motherboard and connect the hosts via an optical fiber network or flat data cables.

(3) Independence from Operating Systems and Processors

Reflective memory cards can be used on various buses such as VME, PCI, PMC, Compact PCI, and Multibus I, allowing computers like ALPHA, Power PC, Macintosh, and Pentium to be connected via a reflective memory real-time network, forming a cluster system.

(4) Deterministic Data Transmission Time

With reflective memory cards, when data is written into the local card's memory, it is simultaneously transmitted to other connected computers without software delays and with minimal hardware latency. Optical fiber reflective memory cards transmit data between nodes in just 400 nanoseconds. This deterministic time delay provides an effective guarantee for designing real-time applications.

(5) Cost-Effective and Efficient

Reflective memory cards offer high data transmission rates without the multiple protocol layers of Ethernet. Additionally, they are easy to use, requiring no development of additional communication software, which enhances system reliability and saves on software development costs.

Implementation Mechanism Based on Reflective Memory Real-Time Network

A reflective memory card is a set of dual-port memory boards. When data is stored in the reflective memory card, the high-speed logic on the board automatically transmits this data along with its address to other reflective memory cards on the network. Data transmission is entirely hardware-driven without CPU intervention, ensuring that the next node on the network has the same data at the same address within 400 nanoseconds. The reflective memory card can be viewed as a unit memory card shared by all nodes on the network, with no access restrictions or arbitration; each node accesses it as if it were local memory, achieving data sharing among nodes.

(1) Data Transmission Method

The reflective memory card can connect up to 256 independent nodes, with a maximum shared memory capacity of 128 MB, data transmission speeds of up to 174 MB/s, and inter-node distances of up to 10 km. Reflective memory cards support interrupts, enabling communication synchronization between node machines through an interrupt mechanism.

(2) Synchronization Using Interrupts

VMIC reflective memory cards support notifying nodes of data reception via interrupts. When data is sent to a node, an interrupt can alert that node. The reflective memory card provides three interrupts, allowing users to define their priority, vector, and specific functions.

(3) Error Management Technology

Reflective memory cards feature error detection and reporting capabilities. By checking the parity bits of data, errors can be detected. The cards also support a redundant transmission mode, where data is transmitted twice each time; if the first transmission fails, the second copy is used.