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Special relays are some relays which are defined with special meanings or functions, start
from SM0.
There are two functions for special relays, first is used to drive the coil, the other type is
forspecial running.
E.g.: SM2 is the initial pulse, activates only at the moment of start
SM34 is “all output disabled”
Special auxiliary relays can’t be used as normal relay M;
Note: The range of soft components mentioned above is the valid range of PLC in the X-NET
communication mode. In the MODBUS communication mode, some relays can not read and
write. The specific usable range is shown in chapter 6-2-3.
2-6 Status Relay (S, HS)
Status relays addresses of XD/XL series PLC are in form of decimal, the address are shown
below:
Status relays S and HS are very import in ladder program; they are used together with
instruction “STL” in the flow. The flow can make the program clear and easy to modify.
For common use
After shut off the PLC power, S relays will be OFF
For Power Off Retentive Use
HS relays can keep the ON/OFF status even PLC power is off
The status relays also have countless “normally ON/OFF” contactors. So users can use
them freely in the program.
Note: The range of soft components mentioned above is the valid range of PLC in the X-NET
communication mode. In the MODBUS communication mode, some relays can not read and
write. The specific usable range is shown in chapter 6-2-3.
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