Rabbit RabbitCore RCM5400W, Руководство пользователя

Страница: 56 / 120

50 RabbitCore RCM4400W
The
USERBLOCK_CLEAR.C
sample program shows you how to clear and write the con-
tents of the user block that you are using in your application (the calibration constants in
the reserved area and the ID block are protected).
5.2.4 SRAM Use
The RCM5400W module has a battery-backed data SRAM and a program-execution
SRAM. Dynamic C provides the
protected
keyword to identify variables that are to be
placed into the battery-backed SRAM. The compiler generates code that maintains two
copies of each protected variable in the battery-backed SRAM. The compiler also generates
a flag to indicate which copy of the protected variable is valid at the current time. This flag
is also stored in the battery-backed SRAM. When a protected variable is updated, the
“inactive” copy is modified, and is made “active” only when the update is 100% complete.
This assures the integrity of the data in case a reset or a power failure occurs during the
update process. At power-on the application program uses the active copy of the variable
pointed to by its associated flag.
The sample code below shows how a protected variable is defined and how its value can
be restored.
main() {
protected int state1, state2, state3;
...
_sysIsSoftReset(); // restore any protected variables
The
bbram
keyword may also be used instead if there is a need to store a variable in
battery-backed SRAM without affecting the performance of the application program. Data
integrity is
not assured when a reset or power failure occurs during the update process.
Additional information on
bbram
and
protected
variables is available in the Dynamic C
User’s Manual .
5.2.5 Wi-Fi Drivers
Complete information on the Wi-Fi libraries and function calls is provided in Chapter 6.
Additional information on TCP/IP is provided in the
Dynamic C TCP/IP User’s Manual .