Echelon Neuron C - Manual (Page 183)

Neuron C Reference Guide 163
connections can still cause changes to such a
configuration network variable.
eeprom The network variable is placed in EEPROM or flash
memory instead of RAM. All variables are placed in RAM
by default. EEPROM and flash memory are only
appropriate for variables that change infrequently, due to
the overhead and execution delays inherent in writing
such memory, and due to the limited number of writes for
such memory devices.
far The network variable is placed in the far section of the
variable space. In Neuron C, variables are placed in near
memory by default, but the near memory areas are
limited in space. The maximum size of near memory
areas is 256 bytes of RAM and 255 bytes of EEPROM, but
could be less in some circumstances.
offchip This keyword places the variable in the off-chip portion of
the variable space. By default, the linker places variables
in either space as it chooses, depending on availability. If
the requested memory is not available, the link fails.
onchip This keyword places the variable in the on-chip portion of
the variable space. By default, the linker places variables
in either space as it chooses, depending on availability. If
the requested memory is not available, the link fails.
uninit This keyword prevents compile-time initialization of
variables. This is useful for eeprom variables that should
not or need not be written by program load or reload.
A different mechanism, subject to your network
management tool, is used to determine whether
configuration properties, including configuration network
variables, are initialized after loading or commissioning
the device. The uninit keyword cannot be used to prevent
configuration network variables from being initialized by
the network management tool. See your network tool's
documentation for details.
Network Variable Types (type)
A network variable can be declared using any of the following types:
• A standard network variable type (SNVT) as described in Chapter 3, How
Devices Communicate Using Network Variables, of the Neuron C
Programmer's Guide . Use of a SNVT promotes interoperability. See
types.lonmark.org for a list of SNVTs.
• A user network variable type (UNVT) as described in Chapter 3, How
Devices Communicate Using Network Variables, of the Neuron C
Programmer's Guide. UNVTs are defined using the NodeBuilder
Resource Editor as described in the NodeBuilder FX User’s Guide.
• Any of the variable types specified in Chapter 1, Overview, of the
Neuron C Programmer's Guide , except for pointers. The types are those
listed below: