6 Functional Description of the Ethernet Modules
6-5
6.2 10Base2 module EI 801F
When using the Ethernet module EI 801F together with the CPU
board PM 803F no battery buffering is ensured. Use the module
EI 811F instead.
6.2.1 Concept
This section aims at giving you some module-specific characteris-
tics. For general features and handling instructions that are com-
mon to all Ethernet modules please refer to Section 6.1.
The 10Base2 module is designed for connecting the AC 800F to the
system bus. It is to be used for:
• networks within a building
• small size installations
• networks with only few nodes
• installations with low EMI and low potential differences
• installations powered by the same low-voltage power source
Besides the communication interface complying with the Ethernet
standard, a so-called MAU (Medium Access Unit) - better known as
a "transceiver" - is located on the module.
With this the EI 801F module is suitable for direct connection of a
thin coaxial cable (also called Cheapernet cable or thin-wire cable).
The only additional part required is a 10Base2 F-connector type for
connecting the coaxial bus into the circuit or for connecting a termi-
nating resistor.
The built-in transceiver provides for electrical isolation between the module hardware
and the Ethernet bus.
A LAN controller is the heart of the 10Base2 module. Its special hardware interface is
adapted to the CPU board processor in an optimal way. The LAN controller provides
for the entire preprocessing of the transmit and receive data in accordance with the
Ethernet standard. As a result, only the net data is communicated through the CPU
board (via DMA), and a considerable load is taken off the main processor. The syn-
chronization with the main processor is realized through the DMA control signals and
interrupt signals.
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