6. Redundancy with NX3030 CPU
275
cycle, through the synchronism channels NETA and NETB. On the other hand, non-redundant
variables aren’t copied between half-clusters, thus can have different values in PLCA and PLCB.
The non-redundant variables are used to store private information of each half-cluster (PLCA or
PLCB), such as module diagnostics inside the half-cluster, including the redundancy diagnostics
(half-cluster diagnostics state, etc.).
The redundant variables regard the shared information connected to the process control. The
variables associated to the I/O modules are typical examples of redundant variables.
Redundant and Non-redundant %I Variables
The NX3030 CPU allocates 96 kbytes of %I variables (%IB0 ... %IB98303).
The first 82 kbytes can be redundant (%IB0 ... %IB81919). The last 16 kbytes are always non-
redundant (%IB81920 ... %IB98303).
The 80 kbytes area which can be redundant is allocated for inputs, which can be read from an I/O
remote module (PROFIBUS, Modbus, etc.).
The 16 kbytes non-redundant area is allocated for a half-cluster “quick private diagnostics”, and also
for the redundancy command panel PX2612 buttons. Quick diagnostics are the ones that must be
updated each MainTask cycle.
The user may configure the redundant %I variables quantity, between 0 and 81920 Kbytes, in 1kbyte
multiples (o valor default é 16384 bytes - %IB0 ... %IB16383). The proper configuration of
redundant %I from %IB0 is important to decrease the necessary time for redundant variables
synchronization (decrease the redundancy overhead). E.g. if the real application allocates only %IB0
... %IB1499 for redundant inputs, the redundant %I area size can be defined as 1500 bytes
The figure below illustrates the redundant and non-redundant %I direct representation variables
allocation, where RI is the %I quantity really configured as redundant
Figure 6-7. Redundant and Non-redundant %I Allocation
Reserved for
redundant %I
expansion
RI kbytes
RI = 0 ... 80
RI default = 16
To Next Page
Loading...
General