# Communication

## Communication

### 1. Fieldbus

1. the **name** of a **family** of industrial computer network **protocols**
2. real-time distributed control
3. IEC 61158

Example: (1) Profibus, (2) EtherCAT, (3) Modbus

#### 1.1. EtherCAT

EtherCAT® is an Ethernet-based fieldbus system, invented by Beckhoff Automation.

Standard PC(TwinCAT) <--\[TCP/IP]--> EtherCat Master(TwinCAT) <--\[EtherCat]--> EtherCat Slave

Standard PC(PyADS) <--\[TCP/IP]--> EtherCat Master(TwinCAT) <--\[EtherCat]--> EtherCat Slave

[http://www.autooo.net/utf8-classid123-id53533.html](https://www.gitbook.com/book/jasonychuang/automation/edit)

<http://www.ethercat.org/pdf/cn/EtherCAT_Introduction.pdf>

**1.1.1. TwinCAT**

The TwinCAT software is the **master application** for EtherCAT.

### 2. Interface

#### 2.1. Automation Device Specification (ADS)

1. device-independent
2. **fieldbus**-independent interface

device <-> ADS <-> Message Router (TCP/IP) <-> ADS <-> device

**2.1.1. ADS device identification**

**AdsPortNr:**

ADS devices in a TwinCAT message router are uniquely identified by this.

**AdsAmsNetId:**

Every PC on the network can be uniquely identified by a TCP/IP address, such as "172.1.2.16". The AdsAmsNetId is an extension of the TCP/IP address and identifies a TwinCAT message router, e.g. "172.1.2.16.1.1".

## Q\&A

1. where are EtherCat Master? @PC, or @plc-controller
2. where is ADS? PC <-> PLC?

## Useful link

EasyCat: <http://www.bausano.net/en/hardware/ethercat-e-arduino/easycat.html>

<http://jayextmemo.blogspot.de/2014/09/ethercat-raspberry-pi-asda-a2.html>
