FB_EXCH: Exchange Function Block
The following graphic shows the pin diagram of the function block FB_EXCH:
The M221 controller can communicate with a Modbus slave device or can send/receive messages in character mode (ASCII).
Twido and EcoStruxure Machine Expert - Basic provide the following functions for communication:
oEXCH instruction to transmit/receive messages
oExchange control function block (MSG) to control the data exchanges
The TwidoEmulationSupport library handles the communication with the function block FB_EXCH. This function block uses the function block SEN.SEND_RECV_MSG of the PLCCommunication library. This has the functionality to send and receive user-defined messages and waits for a response.
The table describes the input variables of the function block in the TwidoEmulationSupport library:
|
Input |
Data Type |
Description |
|---|---|---|
|
i_xExecute |
BOOL |
The functionality starts on rising edge. |
|
i_xReset |
BOOL |
The current message transmission stops on rising edge and the communication reinitializes. |
|
i_byPort |
BYTE |
[1..3] communication port 1 = Serial port 1 2 = Serial port 2 3 = Ethernet |
|
i_pbyBuffer |
POINTER TO BYTE |
Pointer to send and/or receive buffer. The first 2 words are control words. First 2 words: 4 control bytes: 1.Control byte length: The length byte contains the length of the transmission table in bytes (250 maximum), which is overwritten by the number of characters received at the end of the reception (if reception is requested). 2.Control byte command: [0..2] 0 = Transmission only 1 = Send/receive 2 = Reception only 3.Control byte SndBytePosDiscard: Byte position is not sent. 4.Control byte RcvBytePosDiscard: Received byte position is discarded. |
|
i_uiLengthInByte |
UINT |
Length of send/receive buffer + 2 control words |
|
i_xAsciiMode |
BOOL |
TRUE = ASCII mode configured. FALSE = Modbus TCP configured. |
The table describes the output variables of the function block in the TwidoEmulationSupport library:
|
Output |
Data Type |
Description |
|---|---|---|
|
q_xBusy |
BOOL |
q_xBusy is set to TRUE while the function is ongoing. |
|
q_xDone |
BOOL |
q_xDone is set to TRUE when the function is completed successfully. |
|
q_xError |
BOOL |
q_xError is set to TRUE when the function stops because of a detected error. |
|
q_etExchDiag |
ET_ExchDiag |
Diagnostic code. |
|
q_sMsg |
STRING [80] |
Diagnostic message. |
The function block FB_EXCH has the following error codes:
