TwinCAT ADS Interface PLC
The PLC software can be described as a virtual field unit (Automation Device), since it is a pure software PLC. It therefore provides a Beckhoff ADS (Automation Device Specification) interface for other communication partners (e.g. other virtual field units or Windows programs), via which it can be parameterised or interrogated. Use of the ADS standardises access to the PLC and incorporates it into the range of available virtual field units.
The READ and WRITE operations take place on the PLC interface (as defined by ADS) via two numbers: the index group (16 bit) and the index offset (32 bit). The ADS interface of the PLC will be described in more detail in the following pages with regard to the group and offset indices.
Specification "Index-Group" of the PLC
The four global ranges of an ADS unit are shown as follows for the PLC as four sections in the index groups:
Index-Group (0x = hex) | Index Group description |
|---|---|
0x00000000 0x00000FFF | reserved |
0x00001000 | PLC ADS parameter range |
0x00002000 | PLC ADS status range |
0x00003000 | PLC ADS unit function range |
0x00004000 | PLC ADS services ( includes services to access PLC memory range (%M field) ) |
0x00006000 0x0000EFFF | reserved for PLC ADS extension |
0x0000F000 0x0000FFFF | general TwinCAT ADS system services ( includes services to acces PLC process diagramm of the physical inputs and outputs ) |