# NDM Signal Tables

For the EtherNet/IP and PROFINET protocols, the virtual signal table implemented by the NDM is divided into a status table, which contains signals that are modified by the vision application, and a control table, which contains signals that are modified by the PLC. The vision application modifies signals in the status signal table by invoking NDM notification functions, and it is notified of changes to signals in the control signal table when NDM events are invoked. The PLC simply reads and writes the memory locations that correspond to the signal values in the two tables.

The status and control tables are further partitioned into a system region, an engine section, and a data section.

- The system region contains signals that are related to the overall state of the NDM, such as online and offline state.
- The engine region contains four identical blocks of memory that correspond to the four cameras and inspection jobs that can be run concurrently on the vision system.
- The data section contains data written from the vision system to the PLC (inspection results) and from the PLC to the vision system (user data).

The following signal table maps describe the overall organization of both the status and control signal tables.

Note:

The specific memory layout on your PLC depends on the protocol and PLC type:

- For EtherNet/IP PLCs, the signal table layout corresponds exactly to the memory layout on the PLC.
- For PROFINET PLCs, the memory layout is described in the supplied GSD file.
- For Mitsubishi PLCs, the signal table groups the NDM signals into four blocks. Each block contains only single bit signals, or signals that take up an entire word.