Omron SYSMAC C Series User Manual page 109

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Assignment of I/O channel and
relay numbers
Note:
The ON time of a 0.1s clock is 50ms. If a longer time is required for
program execution, the CPU may fail to read the clock.
Relay 1901
This relay is used to generate a 0.2s clock. When used in conjunction with
a counter, it functions as a long-time timer that can retain its present value
during power failure.
Relay 1902
Relay 1903
This relay turns ON when the result of an arithmetic operation is not output
in BCD form.
Relay 1904
This relay serves as a carry flag and operates or releases according to
the result of an arithmetic operation. It can be forcibly turned ON by the
SET CARRY (STC) instruction and turned OFF by the CLEAR CARRY
(CLC) instruction.
Relay 1905
This relay turns ON if the result of the COMPARE (CMP) instruction is ">"
(more than).
Relay 1906
This relay turns ON if the result of the compare operation is "=" (equal to).
it may also turn ON if the result of an arithmetic operation is 0.
Relay 1907
This relay turns ON if the result of the compare operation is "<" (less
than).
Relays TRO to 7
These are temporary memory relays and may not necessarily be
assigned in sequence. The same coil number of these relays must not be
used in duplicate within the same block of a program. However, the same
coil number can be used in a different block. When using a temporary
memory relay, the letters "TR" must be prefixed to the relay number (¢.g.,
TRO).