User`s manual

User’s Manual 39
5.2 Dynamic C Function Calls
5.2.1 Digital I/O
The RCM3200 was designed to interface with other systems, and so there are no drivers
written specifically for the I/O. The general Dynamic C read and write functions allow
you to customize the parallel I/O to meet your specific needs. For example, use
WrPortI(PEDDR, &PEDDRShadow, 0x00);
to set all the Port E bits as inputs, or use
WrPortI(PEDDR, &PEDDRShadow, 0xFF);
to set all the Port E bits as outputs.
When using the external I/O bus on the Rabbit 3000 chip, add the line
#define PORTA_AUX_IO // required to enable external I/O bus
to the beginning of any programs using the external I/O bus.
The sample programs in the Dynamic C SAMPLES/RCM3200 directory provide further
examples.
5.2.2 SRAM Use
The RCM3200 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 creates a backup copy of
a protected variable before the variable is modified. If the system resets while the protected
variable is being modified, the variable's value can be restored when the system restarts.
The sample code below shows how a protected variable is defined and how its value can
be restored.
protected nf_device nandFlash;
int main() {
...
_sysIsSoftReset(); // restore any protected variables
The bbram keyword may also be used instead if there is a need to store a variable in bat-
tery-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.