Echelon Neuron C - Manual (Page 123)

Neuron C Programmer’s Guide 111
This expression uses the network variable’s member identifier, not the network
variable’s unique name. Using the context expression to identify a member
network variable therefore promotes modular device design and reuse of code –
multiple functional blocks implementing the same functional profile can all
implement the same network variable members, although each block’s members
are mapped to a different network variable.
Finally, the properties of the functional block’s network variable members can
also be accessed through an extension of this syntax. The syntax for accessing a
functional block’s member’s property is shown below (the fb-context syntactical
element is defined above):
fb - context :: member - identifier :: property - identifier [ [ index - expr ] ]
Example:
#define NUM_AMMETERS 3
SCPTmaxSndT cp_family cpMaxSendTime;
SCPTminSndT cp_family cpMinSendTime;
SCPTgain cp_family cpGain[4];
SCPTupdateRate cp_family cpUpdateRate;
network output SNVT_amp nvoAmpere[NUM_AMMETERS]
nv_properties
{
cpMaxSendTime,
cpMinSendTime
};
fblock SFPTopenLoopSensor {
nvoAmpere[0] implements nvoValue;
} fbAmpereMeter[NUM_AMMETERS] external_name("AmpereMeter")
fb_properties
{
cpGain, // Each property is an array [4]
static cpUpdateRate
};
All of the following constructs are examples for valid code:
nvoAmpere[2] = 123;
fbAmpereMeter[2]::nvoValue = 123;
fbAmpereMeter[0]::cpGain[i].multiplier = 2L;
nvoAmpere[2]::cpMaxSendTime.seconds = 30;
fbAmpereMeter[2]::nvoValue::cpMaxSendTime.hour = 0;
z = ((SCPTmaxSndT *)&nvoAmpere[2]::cpMaxSendTime)->day;
Pointers can be used with CP family members as shown; however, the
configuration properties are stored in EEPROM. This causes the compiler to
apply special rules as described for the #pragma relaxed_casting_on directive in
the
Neuron C Reference Guide .
Because cpGain is a static configuration property, the following expression is
always true:
fbAmpereMeter[0]::cpGain[i].multiplier ==
fbAmpereMeter[1]::cpGain[i].multiplier
The following expressions are incorrect and cause a compiler error:
// '.' instead of '::'
fbAmpereMeter[0].cpGain[i].multiplier = 123;