Copyright 2007
2-1
S SC150e HARDWARE REFERENCE
2. SCRAMNET OVERVIEW
2.1 Overview
The S SC150e Network is a real-time communications network, based on a
replicated, shared-memory concept. Each host processor on the network has access to its
own local copy of shared memory that is updated over a high-speed, serial-ring network.
The network is optimized for high-speed data transfer among multiple, real-time
computers all solving portions of the same real-time problem.
2.2 Shared Memory
In its simplest form, the S SC150e Network system is designed to appear as
general-purpose memory. The use of this memory depends only on the conventions and
limitations imposed by the specific host computer system and operating system. On most
processors, this means that the application program can use this memory in basically the
same way as any other data-storage area of memory. However, the memory cannot be
used as instruction space.
The major difference between S SC150e memory and system memory is any
data written into S SC150e memory is automatically sent to the same
S SC150e memory location in all nodes on the network. This is why it is also
referred to as replicated shared memory. A good analogy is the COMMON AREA used
by the FORTRAN programming language. Where the COMMON AREA makes variables
available to subroutines of a program, S SC150e makes variables available to
processors of a network.
When a host computer writes to the shared memory, the proper handshaking logic is
supplied by the S SC150e node host adapter. The shared memory behaves
somewhat like resident or local memory.
A software driver is usually not required except for interrupt handling.
2.2.1 Dual-Port Memory Controller
The Dual-Port Memory Controller (see Figure 2-1) allows the host to read from or write
to shared memory with a simultaneous network write to shared memory. Unless an
interrupt has been authorized for that memory address, the host is not aware the network
is writing to shared memory. This is why caching must be disabled for SCRAMNet
memory. If an interrupt has been authorized, the interrupt will then be sent to the host
processor.
Summary of Contents for SCRAMNet+ SC150e
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