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3-1 Introduction
3-1-1 Data Area Overview
Details, including the name, size, and range of each area are summarized in the
following table. Data and memory areas are normally referred to by their acro-
nyms, e.g., the IR Area, the SR Area, etc.
Area Size Range Comments
Internal Relay Area 1 3,776 bits IR 000 to IR 235 Refer to 3-1-2 IR/SR Area Overview and 3-3 IR
(Internal Relay) Area for more details.
Special Relay Area 1 312 bits SR 236 to SR 255
Refer to 3-1-2 IR/SR Area Overview and 3-4 SR
Special Relay Area 2 704 bits SR 256 to SR 299
(Special Relay) Area for more details.
Internal Relay Area 2 3,392 bits IR 300 to IR 511 Refer to 3-1-2 IR/SR Area Overview and 3-3 IR
(Internal Relay) Area for more details.
Temporary Relay Area 8 bits TR 00 to TR 07 Used to temporarily store and retrieve execution
conditions when programming certain types of
branching ladder diagrams.
Holding Relay Area 1,600 bits HR 00 to HR 99 Used to store data and to retain the data values
when the power to the PC is turned OFF.
Auxiliary Relay Area 448 buts AR 00 to AR 27 Contains flags and bits for special functions. Re-
tains status during power failure.
Link Relay Area 1,024 bits LR 00 to LR 63 Used for data links in the PC Link System.
(These bits can be used as work words or work
bits when not used in the PC Link System.)
Timer/Counter Area 512 counters/
timers
TC 000 to TC 511 Used to define timers and counters, and to
access completion flags, PV, and SV.
TIM 000 through TIM 015 are refreshed via
interrupt processing as high-speed timers.
Data Memory Area
6,144 words DM 0000 to DM 6143 Read/Write
DM 6031 is used for indirect DM addressing and
EM bank information and should not be written
by the user.
1,000 words DM 0000 to DM 0999 Normal DM.
2,600 words DM 1000 to DM 2599 Special I/O Unit Area
3,400 words DM 2600 to DM 5999 Normal DM.
31 words DM 6000 to DM 6030 History Log
(44 words) DM 6100 to DM 6143 Link test area (reserved)
Fixed DM Area
512 words DM 6144 to DM 6599 Fixed DM Area (read only)
56 words DM 6600 to DM 6655 PC Setup
Extended Data Memory
Area
6,144 words EM 0000 to EM 6143 The amount of EM area memory depends on the
PC model being used. PCs are available with no
EM, one 6,144-word bank, or three 6,144-word
banks.
Like DM, the EM memory can be accessed in
word units only and EM area data is retained
when the power to the PC is turned OFF.
Work Bits and Words When some bits and words in certain data areas are not being used for their in-
tended purpose, they can be used in programming as required to control other
bits. Words and bits available for use in this fashion are called work words and
work bits. Most, but not all, unused bits can be used as work bits. Those that can
be used are described area-by-area in the remainder of this section. Actual ap-
plication of work bits and work words is described in Section 4 Writing and Input-
ting the Program.
Flags and Control Bits Some data areas contain flags and/or control bits. Flags are bits that are auto-
matically turned ON and OFF to indicate particular operation status. Although
Introduction Section 3-1