Omron SYSMAC CVM1 Series Operation Manual page 79

DM and EM Areas
Indirect Addressing
the CPU Unit in order for the EM Area to be used. There are three models of
Memory Units available, with 64K words (E00000 to E32765 × 2 banks), 128K
words (E00000 to E32765 × 4 banks), and 256K words (E00000 to E32765 × 8
banks).
When the PC is turned on, the EM bank number is automatically set to 0, but can
be changed with the EMBC(171) instruction.
When using the SYSMAC NET Link or SYSMAC LINK systems, D00000
through D00127 are automatically allocated as part of the Data Link Table un-
less data link are set manually from the SSS. The 1,600 words from D02000 to
D03599 are allocated for CPU Bus Units, 100 words for each Unit. The particular
function depends on the type of CPU Bus Unit being used. Refer to the CPU Bus
Unit's Operation Manual for details.
Note D02000 to D03599 are not used by SYSMAC BUS/2 Remote I/O Master Units.
Although composed of 16 bits just like any other word in memory, DM and EM
words cannot be specified by bit for use in instructions with bit-size operands,
such as LD, OUT, AND, and OR, nor can DM words be used with the SHIFT
instruction.
The DM and EM Areas retain status during power interruptions.
Normally, when the content of a data area word is specified for an instruction, the
instruction is performed directly on the content of that word. For example, sup-
pose CMP(020) (COMPARE) is used in the program with CIO 0005 as the first
operand and D00010 as the second operand. When this instruction is executed,
the content of CIO 0005 is compared with that of D00010.
It is also possible, however, to use indirect DM and EM addresses as operands
for instructions. If *D00100 is specified as the data for a programming instruc-
tion, the asterisk in front of D indicates that it is an indirect address that specifies
another which contains the actual operand data. Likewise, EM indirect addres-
sing is indicated by an asterisk in front of the E, *E. When addressed indirectly,
the content of *D00100 can be read as either BCD or binary (hexadecimal) data,
depending on the PC Setup for indirect addressing.
If the content of *DM (or *EM) addresses is defined as BCD in the PC Setup, the
number indicates another DM (or EM) address. If the contents of the *DM ad-
dress are not BCD, a *DM BCD error will occur, and an error flag, A50003, will be
turned ON. Because only the last four digits of the final address can be specified
in one word, the range of possible BCD numbers is #0000 to #9999, and the
range of DM addresses that can be addressed indirectly is D00000 to D09999.
If the content of D00100 is #0324, then *D00100 indicates D00324 as the word
that contains the desired data, and the content of D00324 is used as the operand
in the instruction. The following shows an example of this with the MOVE instruc-
tion.
(030)
MOV *D00100
Word
A090
D00099
D00100
Indirect
D00101
address
D00324
D00325
D00326
Section 3-9
Content
4C59
0324
Indicates
F35A
D00324.
5555
2506
5555 moved
to A0090.
D541
61