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3-6 DM (Data Memory) Area
The DM area is divided into various parts as described in the following table. A
portion of UM (up to 3,000 words in 1,000-word increments) can be allocated as
Expansion DM.
Addresses User
read/write
Usage
DM 0000 to DM 0999 Read/Write Normal DM.
DM 1000 to DM 2599
Special I/O Unit Area
1
DM 2600 to DM 5999 Normal DM.
DM 6000 to DM 6030 History Log
DM 6100 to DM 6143 Reserved
DM 6144 to DM 6599 Read only System Settings
DM 6600 to DM 6655 PC Setup
DM 7000 to DM 9999 Expansion DM
2
Note 1. The PC Setup can be set to use DM 7000 through DM 8599 as the Special
I/O Area instead of DM 1000 to DM 2599. Refer to 3-6-4 PC Setup for de-
tails.
When Special I/O Units are used, 100 words are occupied by each Unit, as
follows:
Unit #0: DM 1000 to DM 1099
Unit #1: DM 1100 to DM 1199
(...)
Unit #9: DM 1900 to DM 1999
Unit #A: DM 2000 to DM 2099
(...)
Unit #F: DM 2500 to DM 2599
2. The UM Area Allocation Programming Console operation can be used to al-
locate up to 3000 words of UM as Expansion DM.
Although composed of 16-bit words like any other data area, data in the DM area
cannot be specified by bit for use in instructions with bit operands. DM 0000 to
DM 6143 can be written to by the program, but DM 6144 to DM 6655 can be over-
written only from a Peripheral Device, such as a Programming Console or com-
puter with SSS.
The DM area retains status during power interruptions.
DM 6031 cannot be used in user applications because it is used by the system to
store EM bank number information and indirect DM addresses.
Indirect Addressing 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 MOV(21) is performed with DM 0100 as the first operand and LR 20 as the
second operand. When this instruction is executed, the content of DM 0100 is
moved to LR 20.
Note Expansion DM cannot be used for indirect addressing.
It is possible, however, to use indirect DM addresses as the operands for many
instructions. To indicate an indirect DM address, DM is input with the address of
the operand. With an indirect address, with content of this operand does not con-
tain the actual data to be used. Instead, its contents is assumed to hold the ad-
dress of another DM word, the content of which will actually be used in the
instruction. If DM 0100 was used in our example above and the content of DM
0100 is 0324, then DM 0100 actually means that the content of DM 0324 is to
DM (Data Memory) Area Section 3-6