This manual describes the DDB (Direct Data Bus) function used to realize data input/output with a
CNC while running a program developed with the user PLC ladder language.
DDB includes the synchronous type (DDBS) and the asynchronous type (DDBA), but only the
asynchronous type will be explained in this manual.
DDB is a function that allows the PLC to directly read and write the various data in the CNC. By
setting the information required for reading and writing into the buffer and calling out the DDB function,
he PLC can set (write) the designated data into the CNC. Generally, the data is read and written in
one piece units, but data related to the control axis can be processed for the designated number of
axes.
Features of this function include that the read data can be referred to in the step immediately following
he execution of the DDBA command. This also applies to the written data.
(Note 1) Note that for the parameters, they may not be valid immediately after writing.
(Note 2) Even for the parameters that will be valid immediately after writing, displaying the screen
again may be required in order to reflect changes to the data displayed on the screen.
(Note 3) The functions related to the specifications not added to the NC cannot be used with the
DDB.
This manual is organized in the following manner after the first chapter. Please refer to the required
section for use.
6. Example of
DDB with
Ladder Circuit
5. Explanation of
Read/write
Data
4. Sub-section
No. List
3. Selection No.
List

2. Usage of DDB
Function with
ladder