Echelon LonTal Stack - Manual (Page 87)

LonTalk Stack Developer’s Guide 75
The maximum number of address table entries that a device could require is
determined by the expected maximum number of different destination entries
that the device requires for connections (network variables and bindable message
tags).
The size of the address table affects the amount of RAM and non-volatile memory
required for the device. When the LonTalk Interface Developer utility calculates
the size of the address table, it attempts to balance the need to limit the amount
of resources required (small address table) and the need for comprehensive
coverage (large address table). Although you generally do not need to, you can
override the automatically calculated value with one that reflects the use of the
device.
Alias Table
An alias is an abstraction for a network variable that is managed by network
management tools and the LonTalk host stack. Network management tools use
aliases to create connections that cannot be created solely with the address and
network variable tables. Aliases provide network integrators with more
flexibility for how devices are installed into networks.
The alias table has no default size, and can contain up to 8192 entries. The
LonTalk Interface Developer utility calculates the size of the alias table. The
utility calculates the required number of alias table entries based on parameters
defined in the device’s interface, such as the number of static network variables
and the number of supported dynamic network variables. The utility always
allocates at least 5 alias table entries, unless the device does not support any
network variables. Within the LonTalk Interface Developer utility, you can
override the automatic calculation of the table size and specify any number of
entries, from 0 to 8192.
The maximum number of aliases that a device could require depends on its
involvement in network variable connections and the characteristics of these
connections. The size of the alias table also affects the performance of the device,
because the alias table must be searched whenever network variable updates
arrive. When the LonTalk Interface Developer utility calculates the size of the
alias table, it attempts to balance the need for performance (small alias table)
and the need for comprehensive coverage (large alias table). Although you
generally do not need to, you can override the automatically calculated value
with one that reflects the use of the device.
Domain Table
The number of domain table entries is dependent on the network in which the
device is installed; it is not dependent on the application.
The LonTalk Interface Developer utility always allocates 2 domain table entries.
From the command-line interface for the LonTalk Interface Developer utility, you
can override the number of entries. However, 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 will prevent certification.