Communication networks (comm)
[Programmable logic controllers (plc)]

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Detailed Description

Messages are sent from one PLC object to another using PLC code.

The following functions are available to send and receive messages.

•  void SNDMSG(char *destination, char *string); 
  

  is used to send a string message to a PLC object.

•  void SNDDAT(char *destination, void *buffer, unsigned int size); 
  

  is used to send a binary message to a PLC object.

•  int RCVMSG(char source[], char buffer[]); 
  

  is used receive a string messages from a PLC object. The buffer must be an array for which sizeof() returns the correct maximum length.

•  int RCVDAT(char source[], void *buffer, unsigned int size); 
  

  is used to receive a binary message from a PLC object.

Each communications networks is defined by a single object that handles all messages between PLC objects linked to it. The network has the following properties

• latency defines the message delivery latency (note this is a functional distribution).
• reliability to define the probability with which a message is delivered at all, and
• bitrate to define the data rate at which messages are delivered (longer messages take longer to be delivered if bitrate is non-zero),

Classes
class	comm
class	Message
class	Queue
Functions
void	Queue::add (Message *msg)
	comm::comm (MODULE *mod)
	Register the new object class and construct the default object properties.
int	comm::create ()
	Create a new object.
EXPORT int	create_comm (OBJECT **obj, OBJECT *parent)
Message *	Queue::drop (Message *msg, bool reverse=false)
int	comm::init (OBJECT *parent)
	Initialize the new object.
EXPORT int	init_comm (OBJECT *obj)
Message *	Queue::next (Message *msg)
TIMESTAMP	Queue::next_delivery_time (void)
Message *	Queue::peek (void)
	Queue::Queue ()
static void	comm::route (comm *net, Message *msg)
TIMESTAMP	comm::sync (TIMESTAMP t0)
	Synchronize the object.
EXPORT TIMESTAMP	sync_comm (OBJECT *obj, TIMESTAMP t0)
Message *	Queue::take (Message *msg=NULL)
	Queue::~Queue ()
Variables
static comm *	comm::defaults = NULL
	a pointer to the default values for new objects
static CLASS *	comm::oclass = NULL
	a pointer to the registered object class definition

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GridLAB-D^TM Version 1.0

An open-source project initiated by the US Department of Energy