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instructions that control bit status, e.g., the OUTPUT, DIFFERENTIATION UP,
and KEEP instructions.
Output Bit Usage Output bits are used to output program execution results and can be used in any
order in programming. Because outputs are refreshed only once during each
cycle (i.e., once each time the program is executed), any output bit can be used
in only one instruction that controls its status, including OUT, KEEP(11),
DIFU(13), DIFD(14) and SFT(10). If an output bit is used in more than one such
instruction, only the status determined by the last instruction will actually be out-
put from the PC.
See 5-15-1 Shift Register – SFT(10) for an example that uses an output bit in two
‘bit-control’ instructions.
Word Allocation for Racks I/O words are allocated to the CPU Rack and Expansion I/O Racks by slot posi-
tion. One I/O word is allocated to each slot, as shown in the following table. Since
each slot is allocated only one I/O word, a 3-slot rack uses only the first 3 words,
a 5-slot rack uses only the first 5 words, and an 8-slot rack uses only the first 8
words. Words that are allocated to unused or nonexistent slots are available as
work words.
←
Left side of rack Right side of a 10-slot rack →
Rack Slot 1 Slot 2 Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 Slot 8 Slot 9 Slot 10
CPU IR 000 IR 001 IR 002 IR 003 IR 004 IR 005 IR 006 IR 007 IR 008 IR 009
1
st
Expansion IR 010 IR 011 IR 012 IR 013 IR 014 IR 015 IR 016 IR 017 IR 018 IR 019
2
nd
Expansion IR 020 IR 021 IR 022 IR 023 IR 024 IR 025 IR 026 IR 027 IR 028 IR 029
3
rd
Expansion IR 300 IR 301 IR 302 IR 303 IR 304 IR 305 IR 306 IR 307 IR 308 IR 309
Unused Words Any words allocated to a Unit that does not use them can be used in program-
ming as work words and bits. Units that do not used the words assigned to the
slot they are mounted to include Link Units (e.g., Host Link Units, PC Link Units,
SYSMAC NET Link Units, etc.), Remote I/O Master Units, Special I/O Units,
Group-2 High-density I/O Units, B7A Interface Units, and Auxiliary Power Sup-
ply Units.
In most C200HX/HG/HE PCs, up to sixteen Special I/O Units may be mounted in
any slot of the CPU Rack or Expansion I/O Racks. (A limited number of Special
I/O Units can be installed in Remote I/O Slave Racks, too.) Each Special I/O Unit
is allocated ten words based on its unit number (0 to F).
Up to ten Special I/O Units may be mounted in the C200HE-CPUjj-E and
C200HG/HX-CPU3j-E/4j-E PCs. Each Unit is allocated ten words based on
its unit number (0 to 9).
Unit number I/O words PC Restrictions
0 IR 100 to IR 109
None
1 IR 110 to IR 119
2 IR 120 to IR 129
3 IR 130 to IR 139
4 IR 140 to IR 149
5 IR 150 to IR 159
6 IR 160 to IR 169
7 IR 170 to IR 179
8 IR 180 to IR 189
9 IR 190 to IR 199
Allocation for Special I/O
Units and Slave Racks
IR (Internal Relay) Area Section 3-3