In a system requiring control over nearly kilometer-long distances with non-uniform distribution of N multi-stations, each substation is responsible for controlling one motor to reverse in place. The central control room must monitor all the devices connected to the network.
Previously, PPI networking was used between CNs, and the software's built-in PPI wizard made configuration very convenient, with communication based on RS485 interface. However, SMART’s DB9 port no longer supports PPI communication. Instead, it now supports GET/PUT communication via the Ethernet port, enabling online data exchange between devices.
Two SR30 units are used: one as the host (IP address 192.168.2.200) and the other as the slave (IP address 192.168.2.201). The host program is designed to handle the main control logic, while the slave program manages the corresponding outputs.
The host program includes logic that detects the rising edge of I0.0 and sends a value of 255 to VB0, which represents all 8 bits being set to 1. This data is then mapped via the configured PUT instruction to the slave’s QB0, causing its Q0.0–Q0.7 to output. When the falling edge of I0.0 is detected, VB0 is set to 0, and the outputs are turned off.
On the slave side, similar logic is implemented, where the rising edge of I0.0 triggers the host’s QB0 to be updated, allowing the host to control its own outputs. This bidirectional communication allows both the host and the slave to control each other’s outputs based on input signals.
To configure this communication, the GET/PUT wizard in the STEP 7-MicroWIN SMART V2.0 environment is used. The process involves adding two entries—PUT and GET—and mapping memory locations between the master and the slave. Each operation is assigned a name and a comment for clarity.
After configuring the data mapping, the wizard allocates memory space for the communication, which in this case uses 43 bytes (from VB43 to VB85). The configuration also generates a logic control block, a symbol table, and a data block for easy reference and debugging.
Once the programs are downloaded into the respective PLCs, the network connection is established using an Ethernet cable. The host PLC (192.168.2.200) is monitored, and the RX/TX indicator lights up, confirming the communication link. When the red button is pressed (connected to I0.0), the host’s Q0.0–Q0.7 activate, lighting up the LEDs on the slave PLC.
Pressing the green self-reset button (also connected to I0.0) triggers the slave’s rising edge, causing the host’s Q0.0–Q0.7 to light up as well. This confirms that the GET/PUT communication is functioning correctly in both directions.
This setup demonstrates how simple it is to implement Ethernet-based GET/PUT communication between PLCs using the built-in wizard in the STEP 7-MicroWIN SMART V2.0 environment. It provides a reliable and efficient way to manage distributed systems over long distances.
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