ALTUS Nexto NX3004 - Page 285

6. Redundancy with NX3030 CPU
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Figure 6-8. Redundant and Non-redundant %Q Allocation
Redundant and Non-redundant %M Variables
The NX3030 CPU allocates 64kbytes of %M variables (%MB0 ... %MB65535).
All the 65535 bytes can be redundant (%MB0000 ... %MB65535). By default the redundant %M
variables quantity is 0.
The %M variable use must be avoided and the use of symbolic variables preferred (see Redundant
and Non-redundant Symbolic Variables section).
Redundant and Non-redundant Symbolic Variables
Besides the direct representation variables (%I, %Q and %M) which are allocated automatically. The
user can explicitly declare symbolic variables, inside of POUs or GVLs. The maximum size allowed
for redundant symbolic variables allocation is 512kbytes.
ATTENTION:
Symbolic variables must not be confused with AT variables. The AT variables are mere symbolic
names attributed to direct representation variables (%I, %Q and %M), using the “AT” declaration.
Thus, AT variables don’t allocate any symbolic variables memory.
Symbolic variables are redundant in the following cases:
 When declared in POUs from the “program” type created in the user application, exceptionally
the NonSkippedPrg program.
 When declared in GVLs created in the user application and these GVLs marked as redundant.
Symbolic variables aren’t redundant in the following cases:
%Q redundant
outputs
Reservado for
redundant %Q
output
expansion
Non-
redundant %Q
65 kbytes
16 kbytes
RQS kbytes
RQS = 0 ... 65535
RQS default = 16384
65536 - RQS
Redundant
%Q
diagnostics
Reserved for
redundant %Q
diagnostics
expansion
RQD kbytes
RQD = RQS ... 81919
RQD default = 16384
81920 - RQD
96 kbytes
80 kbytes
16 kbytes