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9. Exclusive Commands
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9.4 DDB (Direct Data Bus) ... Asynchronous DDB
The DDB function is used for PLC to directly read/write various pieces of data that controller has. PLC
can read specified data into buffer or write specified data into controller by storing necessary
information for read/write and calling the DDB function. Generally, data is read or written for each
data piece; data concerning the control axes is processed in batch as many as the specified number
of axes.
9.4.1 Basic Format of Command
Control data is set by using MOV command, etc.
ACT
S.DDBA
Rn/Dn
(Note 1)
(Note 1) File registers (Rn) and data registers (Dn) to which the user is accessible can be used as
the asynchronous DDB control data buffer. The file registers (R) to which the user is
accessible are R500 through R549 (not backed up) and R1900 through R2799 (backed
up).
9.4.2 Basic Format of Control Data
Control signal
Large section No.
Sub section No.
Data size
Read/write designated axis,
system designation
Read/write data
(For 1st axis)
(For 2nd axis)
(For 3rd axis)
(For 4th axis)
Rn(Dn)
Rn+1(Dn+1)
Rn+2(Dn+2)
Rn+4(Dn+4)
Rn+5(Dn+5)
Rn+6(Dn+6)
Rn+8(Dn+8)
Rn+10(Dn+10)
Rn+12(Dn+12)
～
～
～
～
(Note 2) If only the 3rd axis is designated
for example, the section for the
3rd axis will be read/write data.
(Note 1) System designation is used for
multi-system specifications.
(Note 1)
Read/write designated axis,
part system designation