Echelon Neuron C - Manual (Page 202)

190 Memory Management
The maximum number of aliases for applications developed with the Mini EVK
Evaluation Kit or the Mini FX Evaluation Kit is 32. The limits for host-based
applications depend on the development product used.
Note: See the
ISO/IEC 14908-1 Control Network Protocol standard for a
description of the alias table.
As a general rule, the alias table should be sized in proportion to the number of
network variables that are likely to require an alias, but you should not allocate
more alias table entries than the application could actually require. Although
network variable aliases provide an important tool to enable versatile network
variable connections, an excessively sized alias table can adversely affect overall
system performance, especially if much of that alias table is unused.
The following rule-of-thumb allows calculation of a starting point for alias table
size, nn :
nn = 0; for nv_count = 0
nn = 10 + ( nv_count / 3 ); for nv_count > 0
Starting with this initial size, the alias table size can be refined based on your
understanding of your application.
Domain Table
By default, the domain table is configured for two domains. Each domain uses 15
bytes of EEPROM (on-chip for Series 3100 devices or offchip for Series 5000
devices). The number of domain table entries is a function of the network where
the device is installed, it is not a function of the application. You can reduce the
size of the domain table using the following compiler directive:
#pragma num_domain_entries 1
Notes:
• See the ISO/IEC 14908-1 Control Network Protocol standard for a
description of the domain table.
• As a general rule, the domain table should be sized to the maximum of 2
entries, if possible. L ON M ARK International requires all interoperable
L ON W ORKS devices to have two domain table entries. Reducing the size
of the domain table to one entry prevents certification.
Allocating Buffers
You can use compiler directives to set certain Neuron firmware memory
resources, such as buffer counts and sizes and receive transaction counts. These
values can be set only during compilation. They cannot be configured at run-
time. Figure 18 on page 191 illustrates where application and network buffers
are used. Application buffers are used between the application and network
processors. Network buffers are used between the network and media access
control (MAC) processors.