Echelon i.LON SmartServer 2.0 - Manual (Page 264)

250 Appendix D – i.LON SmartServer Software License Agreement
void CUFPTfpmTempController::Initialize()]
{]
// Determine FB index by looking at one of the NVs name, [index]
char * nv_name =
(char *)nviTemp.GetDpPropertyAsString(FPM::Dp::cfgUCPTname);
// get NV name
// Get FB index number from name
char * tmp_name;
tmp_name = strtok(nv_name,"[");
tmp_name = strtok(NULL,"]");
iFbNumber = strtol(tmp_name, NULL,10); // convert String to int
printf("UFPTfpmTempController[%i]::Initialize() \n",*iFbNumber);
//enter comment in work routine to indicate when nviTemp is changed
void CUFPTfpmTempController::work()
{
if(Changed(nviTemp))
{
printf("UFPTfpmTempController[%i]::Work()- nviTemp =
*iFbNumber,
*nviTemp);
}
}
42. What is the difference between Local and Global FPM variables?
Local variables are defined and used differently then global variables.
• FPM local variables are local to a FB instance.
o
NVs and CPs are always local variables.
o
A local integer variable named iFbNumber would be defined as:
DECLARE_FB_INSTANCE_LOCAL(int, iFbNumber); // local variable
Each FB instance will have its own iFbNumber that only it can read or write.
• FPM global variables are accessible by all FB instances.
o
All FB instances for a FPM can read and write to this variable.
o
FPM global variables are defined as normal C/CC+ variables and are used by all FB
instances of the FPM. A global integer variable named iCount would be defined as:
int iCount; // global variable
• You should use local variables whenever the data is FB instance related (e.g., FB instance index
number, state information, timer information).
• Always design your FPM assuming that it will be used with multiple FBs.
• If you see erratic behavior from a FB, this may mean that you are using a global variable when
you should be using a local variable.
• See the Echelon Knowledge Base web site for examples.
43. Can a FPM driver have NVs and CPs?