Modelling of Network Communications Stack Software ROM and RAM Requirements

For a typical communications C-language software stack, its size in terms of ROM and RAM will be dependent upon the network properties such as number of nodes, schedules, messages and signals. A lot of this information is part of a more detailed design and during architecture selection only signal and nodal information will be available. Messages and schedule information will be part of a much more detailed part of the design process. The objective of the study described in this paper is to ascertain whether ROM and RAM requirements can be estimated from only node and signal information only as this is the information that tends to be available at the very beginning of the electrical architecture design process. Historical data from a LIN design and its associated communications stack is statistically analysed and used to develop a methodology for ROM and RAM requirement estimation. This type of study is particularly interesting for LIN slave devices as the majority of their software contained within the microcontroller flash ROM will be concerned with the LIN communications and flash ROM has a significant impact upon the unit cost of the microcontroller. The preliminary results from the study shows there is a very good possibility of developing a methodology for estimation of ROM and RAM at the early stages of design. This will be useful for microcontroller selection and cost estimation.