How do you configure PLC memory modules and devices in different network architectures?

1 Memory types and addressing

PLCs have different types of memory, such as input, output, data, program, and system memory. Each type has a specific function and size, and can be accessed by using different addressing methods. Addressing is the way of identifying and locating a memory location or a device on the network. There are two main addressing methods: symbolic and physical. Symbolic addressing uses names or labels to refer to memory locations or devices, while physical addressing uses numbers or codes. Symbolic addressing is easier to read and understand, but requires more memory space and processing time. Physical addressing is more efficient and precise, but harder to remember and debug.

4 Star network example

A star network is a network architecture where each device is connected to a central hub or switch. The hub or switch acts as a mediator and distributor of the data and signals between the devices. A star network is easy to set up and expand, but relies heavily on the hub or switch for communication. If the hub or switch fails, the whole network may collapse. A star network can use Ethernet as a network protocol, which is a widely used and standardized protocol that supports high-speed and high-volume data transmission. Ethernet uses physical addressing, such as MAC addresses, to identify and locate the devices on the network.

5 Ring network example

A ring network is a network architecture where each device is connected to two other devices in a circular loop. The data and signals travel in one direction around the loop, passing through each device until they reach their destination. A ring network is simple and reliable, but has a limited bandwidth and may cause delays or collisions if the data traffic is high. A ring network can use Profibus as a network protocol, which is a popular and versatile protocol that supports multiple communication modes and data types. Profibus uses symbolic addressing, such as device names or identifiers, to refer to the devices on the network.

6 Bus network example

A bus network is a network architecture where each device is connected to a common cable or backbone. The data and signals travel along the cable or backbone, and are received by the devices that have the matching address or identifier. A bus network is cheap and easy to maintain, but has a low security and may suffer from noise or interference if the cable or backbone is long or damaged. A bus network can use Modbus as a network protocol, which is a simple and robust protocol that supports serial and parallel communication and data exchange. Modbus uses physical addressing, such as register numbers or codes, to access the memory locations or devices on the network.