4. Configuration
71
Notes:
Symbol : Protocol remains active and operating normally.
Symbol :Protocol is disabled.
SOE: Sequence of Events protocol (SOE) is not available for NX3004, NX3005 and NX3010 CPU
models.
IEC 60870-5-104: The IEC 60870-5-104 Server protocol is not allowed to NX3005 and NX3010
CPU models.
EtherCAT: The tests were performed using MainTask as EtherCAT bus task. If another task is used,
the protocol will remain active when there’s a breakpoint in MainPrg. EtherCAT protocol is not
available for CPUs NX3004, NX3005 and NX3010, neither for redundant NX3030. For further
information on EtherCAT protocol, consult MasterTool IEC XE User Manual MT8500 - MU299609.
MODBUS Symbol Slave/Server: To keep the protocol communicating when the CPU isn’t in RUN
or after a breakpoint, it’s need to check the option “Keep the communication running on CPU stop”.
Double Points
The input and output double digital points representation is done through a special data type called
DBP (defined in the LibDataTypes library). This type consist basically in a structure of two BOOL
type elements, called OFF and ON (equivalent to TRIP and CLOSE respectively).
In Nexto, variables of this type cannot be associated to digital input and output modules, beingn
necessary the single digital points mapping, BOOL type, and the treatment by application to
conversion in double points.
To futher informations about the double points mapping in the input and ouput digital modules check
the IEC 60870-5-104 Server section of Configuration chapter.
CPU’s Events Queue
The CPU owns an events queue of type FIFO (First IN, First Out) used to store temporarily the
events related to communication points until they are moved to their final destiny.
All communication points events generated in the CPU are directed ant stored in CPU’s queue. This
queue has the following features:
Size: 1000 events
Retentivity : It is not.
Overflow policy: keep the newests
ATTENTION:
In the Nexto PLC, the events queue is stored in a non retenvy memory área (volatile). This way, the
events present in CPU’s queue, which haven't been transmitted yet to the control center, are going to
be lost in a CPU’s eventual power off.
The CPU’s event queue is redundant, that means it is synchronized each cycle between both CPUs,
when is used CPU’s redundancy. Futher information can be found on the section about CPU
redundancy.
The in and out of events in this queue follows the concept of producer/consumer. Producers are those
system elements capable of generate events, adding events in the CPU’s queue, while the consumers
are those system elements which receive and use this events, taking them of the CPU’s queue. The
Figure 4-13 describes this working, including the example of some events consumers and producers.
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