Echelon LonTal Stack - Manual (Page 208)

196 Appendix E: Appendix E
Determining Memory Usage for LonTalk
Stack Applications
Resource Type Bytes Required
Notes:
• SD_length is the length of the self-documentation string for the network
variable
• NV_length is the declared size of the network variable (for
changeable-type network variables, NV_length is the maximum size of
the network variable)
In addition to RAM, L ON W ORKS resources also require memory for constant data.
This constant data must be included in both the total RAM size and the total
flash memory size, because all of the constant data is typically loaded from flash
memory into RAM.
The following table lists the estimated amount of flash memory required for each
type of L
ON W ORKS resource.
Resource Type Bytes Required
Static network variable 24 + SD_length + NV_name_length
Dynamic network variable Dyn_NV_count
Alias Alias_count
Address table entry Address_count
Notes:
• SD_length is the length of the self-documentation string for the network
variable
• NV_name_length is the length of the network variable’s name, as defined
in the device’s model file
• Dyn_NV_count is the number of dynamic network variables that are
defined for the application
• Alias_count is the number of aliases that are defined for the application
• Address_count is the number of address table entries that are defined for
the application
In addition to storing constant data, flash memory stores non-volatile data for the
application, as described in Memory for Non-Volatile Data.
Memory for Non-Volatile Data
A LonTalk Stack application typically has some non-volatile data that it must
maintain across device reset (see Providing Persistent Storage for Non-Volatile
Data). The LonTalk host stack stores only non-volatile data that is in use. For
example, it does not store address table and alias table entries that are not used.
Therefore, the actual amount of non-volatile memory used can be smaller than
the maximum amount required. The example direct flash implementation of the