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some flags can be turned ON and OFF by the user, most flags are read only; they
cannot be controlled directly.
Control bits are bits turned ON and OFF by the user to control specific aspects of
operation. Any bit given a name using the word bit rather than the word flag is a
control bit, e.g., Restart bits are control bits.
3-1-2 IR/SR Area Overview
When designating a data area, the acronym for the area is always required for
any area except the IR and SR areas. Although the acronyms for the IR and SR
areas are given for clarity in text explanations, they are not required, and not en-
tered, when programming.
The IR and SR areas are divided into two 256-word sections; the boundary be-
tween these sections is located in the SR area between SR 255 and SR 256.
When the SR area is used as an operand in an instruction, the operand cannot
cross over this boundary. Also, basic instructions that access bits in the second
section (SR 25600 through IR 51115) have somewhat longer execution times.
Area Range Comments
IR Area 1
I/O Area 1 IR 000 to IR 029 I/O words are allocated to the CPU Rack and
Expansion I/O Racks by slot position.
Group-2 High-density I/O Unit
and B7A Interface Unit Area
IR 030 to IR 049 Allocated to Group-2 High-density I/O Units and to
B7A Interface Units 0 to 9.
SYSMAC BUS and
CompoBus/D Output Area
IR 050 to IR 099 Allocated to CompoBus/D outputs and Remote
I/O Slave Racks 0 to 4.
Special I/O Unit Area 1 IR 100 to IR 199 Allocated to Special I/O Units 0 to 9.
Optical I/O Unit and I/O
Terminal Area
IR 200 to IR 231 Allocated to Optical I/O Units and I/O Terminals.
Work Area IR 232 to IR 235 For use as work bits in the program.
SR Area 1 SR 23600 to SR 25507 Contains system clocks, flags, control bits, and
status information.
SR Area 2 SR 256 to SR 299 Contains flags, control bits, and status informa-
tion. SR 290 to SR 297 are used as I/O words by
MCRO(99).
IR Area 2
I/O Area 2 IR 300 to IR 309 These I/O words are allocated to a third
Expansion I/O Rack by slot position.
Work Area IR 310 to IR 329 For use as work bits in the program.
Group-2 High-density I/O Unit
Area 2
IR 330 to IR 341 Allocated to Group-2 High-density I/O Units.
Work Area IR 342 to IR 349 For use as work bits in the program.
CompoBus/D Input Area IR 350 to IR 399 Allocated to CompoBus/D inputs.
Special I/O Unit Area 2 IR 400 to IR 459 Allocated to Special I/O Units A to F.
Work Area IR 460 to IR 511 For use as work bits in the program.
Note 1. Refer to 3-3 IR (Internal Relay) Area for more details on the IR area.
Refer to 3-4 SR (Special Relay) Area for more details on the SR area.
2. Bits in IR Area 1 and IR Area 2 can can be used in programming as work bits
when not used for their allocated purpose.
3-2 Data Area Structure
When designating a data area, the acronym for the area is always required for
any but the IR and SR areas. Although the acronyms for the IR and SR areas are
often given for clarity in text explanations, they are not required, and not entered,
when programming. Any data area designation without an acronym is assumed
to be in either the IR or SR area. Because IR and SR addresses run consecutive-
ly, the word or bit addresses are sufficient to differentiate these two areas.
Data Area Structure Section 3-2