Extended Data Memory (Em) Area; Extended Data Memory - Omron CJ - 08-2008 Operation Manual

Extended Data Memory (EM) Area

9-16 Extended Data Memory (EM) Area

Specifying EM Addresses
1,2,3...
CPU Bus Units (D30000 to D31599)
Each CPU Bus Unit is allocated 100 words (based on unit numbers 0 to F).
Refer to the Unit's Operation Manual for details on the function of these
words. With some CPU Bus Units such as Ethernet Units, initial settings must
be registered in the CPU Unit's Parameter Area; this data can be registered
with a Programming Device other than a Programming Console.
DM Area for CJ CPU Bus Units
(100 words/Unit)
The EM Area is supported by the CJ1 and CJ1-H CPU Units only. It is divided
into 7 banks (0 to C) that each contain 32,768 words. EM Area addresses
range from E0_00000 to EC_32767. This data area is used for general data
storage and manipulation and is accessible only by word.
Data in the EM Area is retained when the PLC's power is cycled or the PLC's
operating mode is changed from PROGRAM mode to RUN/MONITOR mode
or vice-versa.
Although bits in the EM Area cannot be accessed directly, the status of these
bits can be accessed with the BIT TEST instructions, TST(350) and
TSTN(351).
Bits in the EM Area cannot be force-set or force-reset.
There are two ways to specify an EM address: the bank and address can be
specified at the same time or an address in the current bank can be specified
(after changing the current bank, if necessary). In general, we recommend
specifying the bank and address simultaneously.
1. Bank and Address Specification
With this method, the bank number is specified just before the EM address.
For example, E2_00010 specifies EM address 00010 in bank 2.
2. Current Bank Address Specification
With this method, just the EM address is specified. For example, E00010
specifies EM address 00010 in the current bank. (The current bank must
be changed with EMBC(281) to access data in another bank. A301 con-
tains the current EM bank number.)
The current bank will be reset to 0 when the operating mode is changed
from PROGRAM mode to RUN/MONITOR mode, unless the IOM Hold Bit
(A50012) is ON. The current bank is not changed as the program proceeds
through cyclic tasks and the current bank will be returned to its original val-
ue (in the source cyclic task) if it has been changed in an interrupt task.
Special I/O Unit
CPU Unit
Data trans-
ferred to the
CJ 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.
Section 9-16
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