FRB-200U/200/100 User Manual (Ver.1.3, Jun.2008, fmh-001-12) -----
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1. Introduction
FRnet is a two-wire serial communication bus, wired in a similar manner to an
RS-485. FRnet device connection is achieved using a multi-drop method. Unlike
most communication methods based on RS-485, this new method does not use the
traditional question/answer approach. Instead, it uses a fixed scan time to actively
transmit data. Since there is no need for a CPU to process a communication
protocol, FRnet can achieve high-speed data transmission in an isochronous
manner.
The FRB-200/100 is an isolated FRnet communication card designed for use
in the host computer with a PCI bus, the FRB-200U only support the Universal PCI
bus. The FRB-100 card has one FRnet port whereas the FRB-200U/200 card has
two FRnet ports. Each FRnet port has 8 sender nodes and 8 receiver nodes. That
is, the node address setting is defined as SA0~SA7 and RA8~RA15. Each node
contains 16-bit data, which can be either a DI or DO type depending on what
module you use. Therefore, it can control up to a maximum of 128(16X8) digital
output channels and 128(16X8) digital input channels with a total scan time of
2.88ms for 250kbps or 0.72ms for 1Mbps.
I/O data transmission is controlled by the hardware mechanism of the FRnet
control chip which was developed by ICPDAS. It was designed to provide for the
deterministic high speed communication in a network. This communication
mechanism is dominated by the token-stream, which is generated by the network
manager (SA0). This is located in the FRnet and provides for fixed scan-time and
I/O synchronization capability without the need of any special communication
protocol. Furthermore, special anti-noise circuitry has also been considered and
built into the FRnet control chip to ensure communication reliability.
However, the effectiveness of the FRnet connection depends on and is then
ensured when the correct hardware configurations for the sender address (SA)
and receiver address (RA) on the host controller and the remote module in
the network have been installed properly. In general, the operating principle is
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