Echelon Neuron C - Manual (Page 242)

230 Neuron C Custom System Images
consists of the following:
image .nx Loadable image in Intel hex format
image .nxb Binary version of image .nx
image .sym Symbol table file
Tradeoffs, Advantages, and Disadvantages
The use of custom system images provides you with certain advantages in
exchange for some other disadvantages. Sometimes, it is more appropriate to use
a library, and at other times it is more appropriate to use a custom system image.
These issues are discussed in this section, and also in Appendix B,
Neuron C
Function Libraries , on page 221.
Advantages of a Custom System Image
Use of a custom system image to contain utility routines and constant data tables
can provide the following advantages:
1
Use of a custom system image can speed up compilation, because utility
routines are not recompiled each time.
2 A custom system image can provide encapsulation and reuse—software
engineering techniques which can be used to increase quality and
decrease development time.
3 The custom system image can be constructed once and can be used across
many application programs. This can be particularly helpful in the
scenario where the custom system image is programmed into a ROM or
flash memory for a Neuron 3150 Chip or a 3150 Smart Transceiver, and
one of several different application programs which use the custom
system image are then directed into EEPROM or flash memory by
network load at a later date. This scenario can be used by Neuron C field
compiler users who want to deliver devices with a custom system image
that includes support for the application I/O hardware. This support can
be provided as standard functions that can be called by end-user
application code.
Disadvantages of a Custom System Image
Use of a custom system image has the following disadvantages:
1
The NodeBuilder tool offers no way to debug the contents of a system
image. However, the contents of data objects in a system image can be
examined from the Neuron C debugger, provided that the data is declared
as extern in the application program. Procedures should be fully
debugged prior to placing them in a custom system image. Debugger
function is not affected for application programs that use custom system
images.
2 The NodeBuilder project manager cannot be used to manage the
dependencies of a custom system image on its component files. Keeping
the custom system image up-to-date is left entirely up to the user.