5. CONFIGURATION
MODBUS RTU Server Protocol: the limit
(2)
informed relates to the Ethernet interfaces, which limit the amount of
connections that can be established with other devices through a single Ethernet interface. It is not necessary, nor is it
possible to declare or configure Clients devices in the instance of the MODBUS Server protocol. All Clients devices
will have access to all the mappings made directly in the instance of the MODBUS Server protocol.
Requests by device: Number of requests, such as reading or writing holding registers, which can be configured for each of
the devices (slaves or servers) from Master or Client protocols instances. This parameter does not apply to instances of Slave
or Server protocols.
Simultaneous Requests per Instance: Number of requests that can be simultaneously transmitted by each client protocol
instance or that can be received simultaneously by each server protocol instance. MODBUS RTU protocol instances, Master
or Slave, do not support simultaneous requests.
Simultaneous Requests per Device: Number of requests that can be simultaneously transmitted for each MODBUS server
device, or may be received simultaneously from each MODBUS client device. MODBUS RTU devices, Master or Slave do
not support simultaneous requests.
ATTENTION
Simultaneous requests to a variable associated to communication points, those which support
the SBO operation mode (Select Before Operate), even being received from different devices
are not supported. Once started the selection/operation of a point by a specific device, that
must be finished before this point become able to be commanded by another device.
The protocol IEC 60870-5-104 Server limitations can be watched on table below.
Limitations IEC 60870-5-104 Server
Devices per instance 3
Simultaneous requests per instance 3
Simultaneous requests per device 1
Table 68: Protocol IEC 60870-5-104 Server Limits
Notes:
Devices per instance: Quantity of client devices, of type control center, supported for each IEC 60870-5-104 Server
protocol instance. The limit informed might be smaller because of the CPU total limits (check Table 65).
Simultaneous requests per instance: Quantity of requests that can be received simultaneously by each instance of Server
protocol.
Simultaneous requests per device: Quantity of requests that can be received simultaneously of each IEC 60870-5-104
Client device.
5.5.1. Protocol Behavior x CPU State
The table below shows in detail the behavior of each configurable protocol in Nexto Series CPUs in every state of operation.
CPU operational state
STOP RUN
Protocol Type
After
down-
load,
before
appli-
cation
starts
After the
applica-
tion goes
to STOP
(PAUSE)
After an
exception
Non re-
dundant
or Active
Redundant
in Stand-
by
After a
break-
point in
MainPrg
MODBUS Symbol Slave/Server
Master/Client
MODBUS Slave/Server
Master/Client
96
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