Communication Functions on Premium and Atrium PLCs

At a Glance

These functions allow one device to communicate with another. Certain of these are common to several types of communication channels, others may be specific to a single communication channel.

NOTE: Communication functions are processed asynchronously regarding the application task that was used to activate them. The only exceptions are the telegram send/receive and operation stop functions, which are executed in total synchronization with the execution of the activation task.

Asynchronous Communication Functions

A communication function is asynchronous when it is executed during one or several cycles after the one that activated it.

The following table provides an overview of the communication functions with asynchronous execution:

Function	Role
DATA_EXCH	Send/request receipt of data.
ETH_PORT_CTRL	Activate or deactivate a protocol.
INPUT_BYTE	Read an array of bytes.
INPUT_CHAR	Read a character string.
OUT_IN_CHAR	Send a character string and wait for a response.
OUT_IN_MBUS	Emulate a Modbus master communication from a serial link configured in character mode.
PRINT_CHAR	Write a character string.
READ_ASYN	Read 1 Kbyte of messaging.
READ_GDATA	Read common Modbus Plus data.
READ_VAR	Read standard language objects: internal words and bits, system words and bits, timers, monostables, drums, registers, counters.
SEND_REQ	Send UNI-TE requests.
UNITE_SERVER	Process immediately `READ_VAR` and `WRITE_VAR` requests on Modbus (Immediate server).
WRITE_ASYN	Write 1 Kbyte of messaging.
WRITE_GDATA	Write common Modbus Plus data.
WRITE_VAR	Write standard language objects: internal words and bits, system words and bits.

NOTE: It is recommended that asynchronous functions be triggered on edge and not on state to avoid saturating the communication buffers by sending multiple requests. You are also advised, for the same reason, to manage the activity bit and report words during the execution of each communication function.

Synchronous Communication Functions

A communication function is said to be synchronous when it is wholly executed during the PLC task which activated it.

The following table provides an overview of the communication functions with synchronous execution:

Function	Role
CANCEL	Stop an exchange in progress.
RCV_TLG	Receive a telegram.
SEND_TLG	Send a telegram.

Utility Communication Functions

These functions are executed synchronously. A communication function is said to be synchronous when it is wholly executed during the PLC task which activated it.

The following table provides an overview of the utility communication function:

Function	Role
ADDR	Convert a character string into an address (table of 6 integers) that can be directly exploited by the communication function.