Index And Data Registers (Ir And Dr) - Omron SYSMAC CVM1 Series Operation Manual

Index and Data Registers (IR and DR)

3-10 Index and Data Registers (IR and DR)

Direct Addressing
Indirect Addressing
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If the content of *DM addresses is defined as binary in the PC Setup, the number
indicates a internal I/O memory address. The range of possible binary numbers,
$0000 to $FFFF, allows all memory areas, including EM, to be indirectly ad-
dressed.
If, in this case, the content of D00100 is $0324, then *D00100 indicates internal
I/O memory address $0324, which is CIO 0804 in the SYSMAC BUS/2 Area, as
the word that contains the desired data, and the content of CIO 0804 is used as
the operand in the instruction. The following example shows this type of indirect
addressing with the MOVE instruction.
(030)
MOV *D00100
Indirect addressing can also be used in instructions that require bit operands for
bits in the Core I/O Area ($0000 to $0FFF). These bits are designated by using
the rightmost digits of the memory address as the leftmost three digits of the hex-
adecimal address and adding the bit number as the rightmost digit. For example,
the CIO bit 190000 is designated by $76CA where 76C is the rightmost three
digits of the memory address (CIO word 1900 is $076C) and A is bit 10.
The Index Registers, IR0, IR1, and IR2, which contain a single word of data, are
used for indirect addressing. A "," prefix is included before an Index Register to
indicate indirect addressing, just as the "*" prefix is used to indicate indirect ad-
dressing with DM and EM.
If an Index Register is used as an operand in an instruction without the "," prefix,
the instruction is performed directly on the content of that Index Register, as in
the following example.
(030)
MOV D00000 IR0
If an Index Register is used as an operand in an instruction with the "," prefix, the
instruction is performed on the word at the internal I/O memory address indi-
cated by that Index Register, as in the following example.
Word
A090
D00099
D00100
Indirect
D00101
address
CIO 0512
CIO 0513
CIO 0514
Word Content
D00000 08FC
08FC moved
to IR0.
Section 3-10
Content
4C59
0200
Indicates
F35A
CIO 0512.
5555
2506
5555 moved
to A090.
D541
Word Content
IR0 08FC