Control and status data

The control and status data are located in the first 16 bits of the input and output process image. Communication between the terminal and the controller is controlled via this data.

Status data

Bit position	Name	Meaning		Data type
0	Transmit accepted	The terminal acknowledges receipt of data by changing the state of this bit. Only now new data can be transferred from the controller to the terminal.		BOOLEAN
1	Receive request	By changing the state of this bit, the terminal informs the controller that the DataIn bytes contain the number of bytes displayed in “Input length”. The controller must acknowledge receipt of the data by changing the state of the ReceiveAccepted bit. Only then new data can be transferred from the terminal to the controller.		BOOLEAN
2	Init accepted	0	The terminal is ready again for serial data exchange.	BOOLEAN
2	Init accepted	1	Initialization was completed by the terminal.	BOOLEAN
3	Buffer full	The reception FIFO is full. All incoming data will be lost from this point on!		BOOLEAN
4	Parity error	A parity error has occurred.		BOOLEAN
5	Framing error	A framing error has occurred.		BOOLEAN
6	Overrun error	An overrun error has occurred.		BOOLEAN
7	-
8...15	Input length	Number of input bytes available for transfer from the terminal to the controller.		UINT8

Control data

Bit position	Name	Meaning		Data type
0	Transmit request	By changing the state of this bit, the controller informs the terminal that the DataOut bytes contain the number of bytes displayed in “Output length”. The terminal acknowledges receipt of the data by changing the state of the “TransmitAccepted” bit. Only now new data can be transferred from the controller to the terminal.		BOOLEAN
1	Receive accepted	The controller acknowledges receipt of data by changing the state of this bit. Only then new data can be transferred from the terminal to the controller.		BOOLEAN
2	Init request	0	The controller once again requests the terminal to prepare for serial data exchange.	BOOLEAN
2	Init request	1	The controller requests terminal for initialization. The transmit and receive functions will be blocked, the FIFO pointer will be reset and the interface will be initialized with the values of the responsible Settings object. The execution of the initialization will be acknowledged by the terminal with the ‘Init accepted’ bit.	BOOLEAN
3	Send continuous	Continuous sending of data from the FIFO. The send buffer is filled (up to 128 bytes) by the controller. The filled buffer contents will be sent on the rising edge of the bit. If the data has been transmitted, the terminal informs the controller by setting the “Init accepted” bit. “Init accepted” is cleared with “SendContinuous”.		BOOLEAN
4...7	-
8...15	Output length	Number of output bytes available for transfer from the controller to the terminal.		UINT8

PDO Assignment

The terminal makes two input/output process images available for each channel. These differ only in the representation of the control/status data.

In the case of bitwise representation, the data is made available as shown in the tables above. In the case of word-wise representation, the first 16 bits of the process data are combined in one word.

The process data objects begin as standard with a control/status word. This PDO assignment is required in order to use the ‘TwinCAT PLC Serial Communication’ library.

Status Inputs	Control Outputs	Representation
0x1A00	0x1600	bitwise Ch. 1
0x1A01	0x1601	bitwise Ch. 2
0x1A02	0x1602	bitwise Ch. 3
0x1A03	0x1603	bitwise Ch. 4
0x1A04	0x1604	word-wise Ch 1
0x1A05	0x1605	word-wise Ch 2
0x1A06	0x1606	word-wise Ch 3
0x1A07	0x1607	word-wise Ch 4