Omron CP1E CPU UNIT SOFTWARE User Manual page 80

5 I/O Memory
Applications
The DM Area is for storing numeric data. It can be used for data exchange with Programmable Termi-
nals, serial communications devices, such as Inverters, and Analog I/O Units or Temperature I/O Units.
Details
Bits in the DM Area cannot be addressed individually.
Backing Up to the Built-in EEPROM Backup Memory
• The number of words set in the PLC Setup can be saved to the built-in EEPROM backup memory
during operation by turning ON the DM Backup Start bit (A751.15).
• Specify in the PLC Setup whether to read the data in the DM Area words to the RAM as the initial
values when the power supply is turned ON.
Refer to 16-3 DM Backup Function for how to use DM Area words and bits.
DM Fixed Allocation Words for the Modbus-RTU Easy Master
The following DM area words are used as command and response storage areas with the Modbus-
RTU Easy Master function. These words are used for other applications if the Modbus-RTU Easy
Master function is not served.
Refer to 14-4 Modbus-RTU Easy Master Function for how to use the DM Area words and bits.
Indirect Addressing of the DM Area
Indirect addressing can be used in the DM Area.
There are two modes that can be used.
Binary-mode Addressing (@D)
If a "@" symbol is input before a DM Area address, the contents of that DM Area word is treated as
a hexadecimal (binary) address and the instruction will operate on the DM Area word at that
address.
The entire DM Area can be indirectly addressed with hexadecimal values 0000 to 1FFF.
Example:
@D0
BCD-mode Addressing (*D)
If a * symbol is input before a DM Area address, the content of that DM Area word is treated as a
BCD address and the instruction will operate on the DM Area word at that address.
Only part of the DM Area (D0 to D8192) can be indirectly addressed with BCD values 0 to 8192.
Example:
*D0
5-12
0100 D256
Address actually used.
0100 D100
Address actually used.
CP1E CPU Unit Software User's Manual(W480)