Rockwell Automation 57C570 AutoMax PC3000 User Manual - Manual (Page 39)

3Ć1
3.0 DESIGNING AN AutoMax
DCSĆNET NETWORK
You can use either coaxial or fiberĆoptic cable for the DCSĆNET
network. This chapter provides information to help you design a
DCSĆNET network.
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For information about:
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See this section:
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The AutoMax DCSĆNET Network БББББББ
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3.1
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Choosing the DCSĆNET Network Media БББББББ
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3.2
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Designing a Coaxial Network
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3.3
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Designing a FiberĆOptic Network
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3.4
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Calculating the Data Update Rate
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3.5
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What to Do Next
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3.6
3.1 About the AutoMax DCSĆNET Network
The AutoMax DCSĆNET network is a proprietary network that
connects multiple AutoMax Processors to form a distributed control
system. In addition to connecting AutoMax Processors, you can
connect GV3000 and FlexPak 3000 drives, AutoMax PC3000s, and
PCs that have the PC3000 Processor or PCĆLink cards installed. All
network data is transmitted and received over a single
serialĆcommunication coaxial or fiberĆoptic cable at 875 Kbps.
The network is structured as a master/slave bus. The devices on the
network are called drops." The master drop (drop 0) initiates and
controls all transmissions on the network. All transmissions are
broadcast, i.e., all Network interfaces receive the data packets
simultaneously. An address encoded in each data packet identifies
which slave drop is to respond to that transmission. The slave's
response is also broadcast, with all drops on the network receiving
the response data packet. All messages are checked for correctness.
At powerĆup, the master polls all the slave drops to determine which
drops are active on the network and sets the appropriate bits in its
status registers. The master initiates all transmissions on the network.
During a communication cycle, the master transmits data to each
active drop on the network in sequence.
Each Network interface contains enough dualĆport memory for
storing all data that is transmitted over the network; therefore, each
drop contains a memory image of the latest version of all network
data at all times. This allows each section of the distributed control
system to quickly and easily access data from other sections of the
system. The dualĆport memory image can be accessed by the CPU
on the network interface as well as by any AutoMax Processor.
The dualĆport memory of each Network interface is divided into 56
areas called drop areas. Each drop area contains 64, 16Ćbit registers.
The master drop transmits 32 registers to each slave drop area and
receives 32 registers from each slave drop area. See Figure 3.1.