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Ethernet
A BL67 station can be comprised of the gateway for Ethernet and a maximum of 32
modules (corresponding to a station length of approx. 1 m)
NOTE:
The maximum number of modules is
dependent on the respective system
configuration. The maximum number may
be limited as the maximum current
consumption on the module bus may not
exceed 1.5 A (refer to the rated current
consumption table, page 18). A limitation
may also result if modules with extensive
process, parameter and diagnostic data
are used. The I/O-ASSISTANT takes this
fact into consideration and issues a
warning message if appropriate.
BL67-Station – Maximum System Extension
Digital inputs, 4 DI/DO
Digital inputs, 8 DI/DO
Digital inputs, 16 DO
Analogue inputs, 2 AI
Analogue inputs, 4 AI
Analogue inputs, 2 AI-PT
Analogue inputs, 2 AI-TC
Analogue outputs, 2 AO-I
Analogue outputs, 2 AO-V
128
256
512
64
128
64
64
64
50
32
32
32
32
32
32
32
32
25
Module type Channels
Max. no./station
Modules
Max. no./station
BL67 and Ethernet (Overview)
• Open fieldbus standard acc. to
IEE 802.3
• Transmission medium:
2 x 2 twisted-pair copper cable,
shielded, category 3 (10 Mbps),
category 5 (100 Mbps)
• Bus topology: star structure/
tree structure
• Switches and hubs as
junction points for connection
of the Ethernet nodes
• Bus access mode:
multi-master system
with CSMA/CD access mode,
network-wide multi/broadcasting
• Number of bus nodes theoretically
unlimited
• Protocols: MODBUS TCP,
EtherNet/IP and PROFINET IO
The term Ethernet generally stands for the
IEEE 802.3 specification. The modules are
networked within a tree or star structure
and are marked according to a 6-byte,
worldwide and unique identification code
(MAC ID). The distance between two bus
nodes may not exceed 100 m when using
rigid cables. If flexible cables are used, the
maximum length depends on the network
construction.
Switches and hubs interconnect the
Ethernet nodes and are thus the nodal
points within the network. Hubs always
send data to and receive data from all
nodes, whereas switches feature a selec-
tive data transmission mode. Switches
dynamically govern a list with the IP
addresses of all connected bus nodes.
Thus it is ensured that data are only sent
to the relevant target address. Data
collisions are avoided and the network
bandwidth is increased.
The original Ethernet protocol transfers the
data frame from one to a single or several
other nodes. The transmission mode does
not include acknowledgement messages
(handshake communication) and re-trans-
fer of lost data frames. The Internet
Protocol (IP) handles segmenting, routing
(path finding), searching and allocation of
the permanent MAC-IDs.
Just like the Ethernet protocol, the IP does
not ensure secure data transport. Data
frames can get lost or be disrupted in their
order.
Protocols such as TCP/IP, which ensure
safe data transmission, are available. The
Transmission Control Protocol (TCP) is
based on the IP and is a connection-
orientated transfer protocol, comprising
error diagnostics and error handling
mechanisms. This protocol ensures that
lost telegrams are re-transmitted.
Based on TCP, further protocols such as
MODBUS TCP, EtherNet/IP and
PROFINET IO have been developed for
applications involving industrial data
communication.
Configuration Modbus TCP
The IP address comprises 4 bytes and is
set by the user via three coded rotary
switches on the BL67 module. The
Modbus-TCP port is assigned to 502.
The transmission speed is automatically
detected by the BL67 modules (auto
baud).
System data Ethernet Modbus TCP
Number of I/O stations only limited through IP address area
Number of I/O points depending on control system
Transmission medium 2 x 2 twisted-pair copper cable, shielded, category 3 (10 Mbps), category 5 (100 Mbps)
Line length max. 100 m distance between the modules
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