Control and status word
Control word
The control word (CW) is located in the output process image, and is transmitted from the controller to the terminal.
Bit | CW.15 | CW.14 | CW.13 | CW.12 | CW.11 | CW.10 | CW.9 | CW.8 | CW.7 | CW.6 | CW.5 | CW.4 | CW.3 | CW.2 | CW.1 | CW.0 |
Name | OL7 | OL6 | OL5 | OL4 | OL3 | OL2 | OL1 | OL0 | - | OL2* | OL1* | OL0* | SC | IR | RA | TR |
Bits CW.15 to CW.8 are only shown if the large process image is used.
If the small or medium process image is used, only bits CW.7 to CW.0 are shown as control bytes! The number of output bytes available for transfer from the controller to the terminal is displayed by bits OL2* ... OL0*.
Legend
Bit | Name | Description | |
|---|---|---|---|
CW.15 ... CW8 | OL7 ... OL0 | 1dec... 22dec | If the large process image is used: Number of output bytes available for transfer from the controller to the terminal. |
- | If the small/medium process image is used: not shown | ||
CW.7 | - | 0bin | reserved |
CW.6 ... CW.4 | OL2* ... OL0* | 0 | If the large process image is used: reserved |
1 ... 6 | If the medium process image is used: Number of output bytes available for transfer from the controller to the terminal. | ||
1 ... 4 | If the small process image is used: Number of output bytes available for transfer from the controller to the terminal. | ||
CW.3 | SC | rise | Continuous sending of data from the FIFO. The send buffer is filled (up to 128 bytes) by the controller. The buffer content is sent with rising edge of bit SC. The terminal acknowledges the data transfer to the controller through setting of bit SW.2. SW.2 is cancelled with CW.3. |
CW.2 | IR | 1bin | The controller requests terminal for initialization. The send and receive functions are blocked, the FIFO pointers are reset, and the interface is initialized with the values of the responsible objects (baud rate 4073, data frame 4074, feature bits 4075). The terminal acknowledges completion of the initialization via bit SW.2 (IA). |
0bin | The controller once again requests the terminal to prepare for serial data exchange. | ||
CW.1 | RA | toggle | 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. |
CW.0 | TR | toggle | Via a change of state of this bit the controller notifies the terminal that the DataOut bytes contain the number of bytes indicated via the OL bits. The terminal acknowledges receipt of the data in the status byte via a change of state of bit SW.0 (TA). Only now new data can be transferred from the controller to the terminal. |
Status word
The status word (SW) is located in the input process image, and is transmitted from terminal to the controller.
Bit | SW.15 | SW.14 | SW.13 | SW.12 | SW.11 | SW.10 | SW.9 | SW.8 | SW.7 | SW.6 | SW.5 | SW.4 | SW.3 | SW.2 | SW.1 | SW.0 |
Name | - | - | - | - | - | - | - | - | - | IL2* | IL1* | IL0* | BUF_F | IA | RR | TA |
Name | IL7 | IL6 | IL5 | IL4 | IL3 | IL2 | IL1 | IL0 | - | OVERRUN | FRAMING | PARITY ERR | BUF_F | IA | RR | TA |
If the small or medium process image is used, only bits SW.7 to SW.0 are shown as status bytes! The number of input bytes available for transfer from the terminal to the controller is displayed by bits IL2* ... IL0*.
Legend
Bit | Name | Description | |
|---|---|---|---|
SW.15 ... SW8 | IL7 ... IL0 | 1dec ... 22dec | If the large process image is used: Number of input bytes available for transfer from the terminal to the controller. |
- | If the small/medium process image is used: not shown | ||
SW.7 | - | 0bin | reserved |
SW.6 | IL2* | 0 ... 1 | If the large process image is used: An overrun error has occurred. The affected data item is not loaded into the receive FIFO of the terminal and is lost. |
1 ... 6 | If the medium process image is used: Number of input bytes available for transfer from the terminal to the controller. | ||
1 ... 4 | If the small process image is used: Number of input bytes available for transfer from the terminal to the controller. | ||
SW.5 | IL1* | 0 ... 1 | If the large process image is used: A framing error has occurred. The affected data item is not loaded into the receive FIFO of the terminal and is lost. |
1 ... 6 | If the medium process image is used: Number of input bytes available for transfer from the terminal to the controller. | ||
1 ... 4 | If the small process image is used: Number of input bytes available for transfer from the terminal to the controller. | ||
SW.4 | IL0* | 0 ... 1 | If the large process image is used: A parity error has occurred. The affected data item is not loaded into the receive FIFO of the terminal and is lost |
1 ... 6 | If the medium process image is used: Number of input bytes available for transfer from the terminal to the controller. | ||
1 ... 4 | If the small process image is used: Number of input bytes available for transfer from the terminal to the controller. | ||
SW.3 | BUF_F | 1bin | The reception FIFO is full. All further incoming data will be lost! |
SW.2 | IA | 1bin | Initialization was completed by the terminal. |
0bin | The terminal is ready again for serial data exchange. | ||
SW.1 | RR | toggle | Via a change of state of this bit the terminal notifies the controller that the DataIn bytes contain the number of bytes indicated via the IL bits. The controller has to acknowledge receipt of the data in the control byte via a change of state of bit CW.1 (RA). Only then new data can be transferred from the terminal to the controller. |
SW.0 | TA | toggle | 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. |
Data transfer examples
The examples use the large process image.
- Initialization:
Control word | Status word | Comment | ||
|---|---|---|---|---|
CW.15 ... CW.8 | CW.7 ... CW.0 | SW.15 ... SW.8 | SW.7 ... SW.0 | |
xxxx xxxxbin | xxxx xxxxbin | xxxx xxxxbin | xxxx xxxxbin | Start of data transmission |
0000 0000bin | 0000 0100bin | 0000 0000bin | 0000 0000bin | The controller requests terminal initialization |
0000 0000bin | 0000 0100bin | 0000 0000bin | 0000 0100bin | Command is executed: Terminal initialization is complete |
0000 0000bin | 0000 0000bin | 0000 0000bin | 0000 0100bin | The controller requests the terminal to prepare for serial data exchange |
0000 0000bin | 0000 0000bin | 0000 0000bin | 0000 0000bin | Command is executed: Terminal is ready for serial data exchange |
- Data transfer from the controller to the terminal:
Control word | Status word | Comment | ||
|---|---|---|---|---|
CW.15 ... CW.8 | CW.7 ... CW.0 | SW.15 ... SW.8 | SW.7 ... SW.0 | |
0000 0000bin | 0000 0000bin | xxxx xxxxbin | 0000 x0x0bin | Start of data transmission |
0000 0010bin | 0000 0001bin | xxxx xxxxbin | 0000 x0x0bin | The controller requests transmission of 2 bytes by the terminal |
0000 0010bin | 0000 0001bin | xxxx xxxxbin | 0000 x0x1bin | Command is executed: Terminal has loaded 2 bytes into the transmission FIFO |
0001 0000bin | 0000 0000bin | xxxx xxxxbin | 0000 x0x1bin | The controller requests transmission of 16 bytes by the terminal |
0001 0000bin | 0000 0000bin | xxxx xxxxbin | 0000 x0x0bin | Command is executed: Terminal has loaded 16 bytes into the transmission FIFO |
- Data transfer from the terminal to the controller:
Control word | Status word | Comment | ||
|---|---|---|---|---|
CW.15 ... CW.8 | CW.7 ... CW.0 | SW.15 ... SW.8 | SW.7 ... SW.0 | |
xxxx xxxxbin | 0000 000xbin | 0000 0000bin | 0000 000xbin | Start of data transmission |
xxxx xxxxbin | 0000 000xbin | 0000 0011bin | 0000 001xbin | The terminal requests transfer of 3 bytes from the controller |
xxxx xxxxbin | 0000 001xbin | 0000 0011bin | 0000 001xbin | Acknowledgement: Controller has received 3 bytes from the reception FIFO |
xxxx xxxxbin | 0000 001xbin | 0001 0110bin | 0000 000xbin | The terminal requests transfer of 22 bytes from the controller |
xxxx xxxxbin | 0000 000xbin | 0001 0110bin | 0000 000xbin | Acknowledgement: Controller has received 22 bytes from the reception FIFO |