169
Data Memory Area (D) Section 4-14
Forcing Bit Status Bits in the DM Area cannot be force-set or force-reset.
Indirect Addressing Words in the DM Area can be indirectly addressed in two ways: binary-mode
and BCD-mode.
Binary-mode Addressing (@D)
When a “@” character is input before a DM address, the content of that DM
word is treated as binary and the instruction will operate on the DM word at
that binary address. The entire DM Area (D0 to D32767) can be indirectly
addressed with hexadecimal values 0000 to 7FFF.
BCD-mode Addressing (
*D)
When a “*” character is input before a DM address, the content of that DM
word is treated as BCD and the instruction will operate on the DM word at that
BCD address. Only part of the DM Area (D0 to D09999) can be indirectly
addressed with BCD values 0000 to 9999.
DM Area Allocation to
Special I/O Units
Parts of the DM Area are allocated to Special I/O Units and CPU Bus Units for
functions such as initial Unit settings. The timing for data transfers is different
for these Units, but may occur at any of the three following times.
1,2,3... 1. Transfer data when the PLC’s power is cycled or the Unit is restarted.
2. Transfer data once each cycle.
3. Transfer data when required.
Refer to the Unit’s operation manual for details on data transfer timing.
Special I/O Units (D20000 to D29599)
Each Special I/O Unit is allocated 100 words based on unit numbers 0 to 95.
Refer to the Unit’s operation manual for details on the function of these words.
@D100
D256
0100
▲
Address actually used.
*D100
D100
0100
▲
Address actually used.
DM Area for Special I/O Units
(100 words/Unit)
CPU Unit
Special I/O Unit
Data trans-
ferred to the
Special I/O
unit when the
PLC is turned
ON or the Unit
is restarted.
Data trans-
ferred to the
CPU Unit at
cyclic refresh-
ing or when
necessary.
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