4 • 3-Series Control Systems Reference Guide – DOC. 7150B
The directory structure of a 3-Series control system can reside on the internal
flash memory and on optional external memory (SD/SDHC). Programs, data
files, and data can be stored on either internal or external memory. The files that
reside in the internal flash conform to a flat directory structure, while the
external memory system conforms to a FAT32-compatible file system.
NOTE: Although file system names are case insensitive, the case is preserved to
maintain file checksums.
Observe the following about external media directories:
• The RM and RM2 directories appear only when external removal media is
inserted into the control system. To reference files in external memory,
prefix "\RM\" or "\RM2\" to any fully qualified path from the computer
OS environment.
• When a SIMPL Windows or SIMPL Sharp Pro program is stored in
external memory, the files reside in the "\RM[2]\Simpl\AppXX\" directory,
where XX is the program number.
• When web pages are stored in external memory, the pages reside in the
"\RM[2]\HTML\" directory.
• Storing programs and web pages in external memory gives them
precedence over files stored in internal flash memory. For example, if
different programs are stored in both internal flash and external memory,
the program in external memory will run when the system is booted.
SDRAM (Volatile)
Volatile SDRAM is used by the operating system to dynamically store the
following components:
• Digital and analog signal values
• SIMPL+ variables (default is no options are specified, or if using "volatile"
qualifier or #DEFAULT_VOLATILE)
The actual amount of SDRAM used at any given time depends on the particular
program that is running; therefore, usage is variable (dynamic) during normal
operation.
NVRAM (Nonvolatile)
Nonvolatile NVRAM contain the following components:
• SIMPL+ variables (if "volatile" qualifier or #DEFAULT_VOLATILE is
removed)
• Signals explicitly written to NVRAM (such as Analog RAM, Analog RAM
from database, Serial RAM, Serial RAM from database, Analog
nonvolatile ramp, Digital RAM, and so forth)
NOTE: SIMPL Sharp Pro has no access to the NVRAM. Programmers should write
files for persistent variables instead.