FB_GENIbusCommunication

The function blocks for the GENIbus commands do not directly access the process image of the selected serial interface; instead, they place the individual GENIbus commands into three different buffers. The function block FB_GENIbusCommunication() sequentially reads the GENIbus commands from these three buffers and forwards the GENIbus commands to the serial interface. This prevents multiple function blocks accessing the process image of the serial interface at the same time. Each of these three buffers is processed with a different priority (high, medium or low). The parameter eCommandPriority, which is available for most function blocks, can be used to specify the priority with which the respective GENIbus command is processed by the function block FB_GENIbusCommunication().

The buffers in which the GENIbus commands are placed are all contained in a variable of the type ST_GENIbusCommandBuffer. There is one instance of the function block FB_GENIbusCommunication() and one variable of the type ST_GENIbusCommandBuffer per serial interface. If possible, the function block FB_GENIbusCommunication() should be called in a separate, faster task.

The extent to which the buffers are utilized can be determined from the outputs of the function block. Three arrays are output for this in which each element (0, 1 or 2) represents one of the three buffers (high, middle or low). If you detect regular overflow for one of the three buffers, you should consider the following:

How heavily are the individual PLC tasks utilized? TwinCAT XAE provides suitable analysis tools.
Try reducing the cycle time of the task in which the function block FB_GENIbusCommunication() is called. The value should not exceed 6 ms. Ideally it should be 2 ms.
Check the cycle time of the PLC task in which the function blocks for the individual GENIbus commands are called. This value should be between 10 ms and 60 ms.
If possible avoid polling (regular reading) of values. Only read values when they are actually required.

Inputs

VAR_INPUT
  bResetMaximumDemandCounter    : BOOL;
  bResetOverflowCounter         : BOOL;
  byMasterAddr                  : BYTE;
  dwOptions                     : DWORD := 0;
  eComMode                      : E_GENIbusComMode;
END_VAR

Name	Type	Description
bResetMaximumDemandCounter	BOOL	A rising edge resets the stored value of the maximum command buffer utilization, arrBufferMaximumDemandMeter (0 - 100%, see VAR_OUTPUT).
bResetOverflowCounter	BOOL	A rising edge resets the stored value of the number of command buffer overflows, arrBufferOverflowCounter (see VAR_OUTPUT).
byMasterAddr	BYTE	Specifies the address that the TwinCAT controller should have within the GENIbus line. Possible input range: 0 - 31.
dwOptions	DWORD	Reserved for future applications.
eComMode	E_GENIbusComMode	The selection of the serial communication interface must be entered at this parameter. If a KL terminal or an EtherCAT Terminal is in use, then a configuration of the connection parameters is internally and automatically started: Baud Rate: 9600 Data Bits: 8 Parity: None Stop Bits: 1 Unfortunately this is not possible for PC-based interfaces; in this case the parameters must be directly entered in the TwinCAT XAE.

Inputs/outputs

VAR_IN_OUT
  stInData              : ST_GENIbusInData;
  stOutData             : ST_GENIbusOutData;
  stCommandBuffer       : ST_GENIbusCommandBuffer;
END_VAR

Name	Type	Description
stInData	ST_GENIbusInData	Reference to the structure which contains the input process image for communication with the serial interface.
stOutData	ST_GENIbusOutData	Reference to the structure which contains the output process image for communication with the serial interface.
stCommandBuffer	ST_GENIbusCommandBuffer	Reference to the structure for communication (buffer) with the FB_GENIbusCommunication() function block

Outputs

VAR_OUTPUT
  bBusy                       : BOOL;
  bError                      : BOOL;
  udiErrorId                  : UDINT;
  udiErrorArg                 : UDINT;
  arrBufferDemandMeter        : ARRAY[0..2] OF BYTE;
  arrBufferMaximumDemandMeter : ARRAY[0..2] OF BYTE;
  arrBufferOverflowCounter    : ARRAY[0..2] OF UINT;
  bLineIsBusy                 : BOOL;
  bLineIsInitialized          : BOOL;
  bLineIsConfigured           : BOOL;
END_VAR

Name	Type	Description
bBusy	BOOL	Starting with the edge at bStart, this output remains TRUE until the command has been processed.
bError	BOOL	This output is switched to TRUE as soon as an error occurs during the execution of a command. The command-specific error code is contained in udiErrorId.
udiErrorId	UDINT	Contains the command-specific error code of the most recently executed command (see error codes). It is set back to 0 by the reactivation of the function block via the bStart input.
udiErrorArg	UDINT	If applicable, contains an extended description of the error code.
arrBufferDemandMeter	ARRAY OF BYTE	Demand of the respective buffer (0 - 100%).
arrBufferMaximumDemandMeter	ARRAY OF BYTE	Previous maximum demand of the respective buffer (0 - 100%).
arrBufferOverflowCounter	ARRAY OF UINT	Number of buffer overflows to date.
bLineIsBusy	BOOL	This output is set as long as the serial communication is active.
bLineIsInitialized	BOOL	If the function block is called up for the first time (e.g. when starting the controller), initialization is carried out. No GENIbus commands can be processed during this time.
bLineIsConfigured	BOOL	This output indicates with TRUE that the terminal has been successfully configured with the above-mentioned serial parameters. This output is automatically set if the interface is a PC interface, since the user has to enter the parameters himself in the TwinCAT XAE.

	Since an error may not interrupt the execution of the function block, bError, udiErrorId and udiErrorArg are initially reset in every PLC cycle and then re-evaluated.

Requirements

Development environment	PLC library to include
TwinCAT from v3.1.4020.14	Tc2_GENIbus from v3.3.0.0