Chapter 5 Relay Ladder Logic Programming 67
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Auxiliary Coils ( M )
Auxiliary Coils are the virtual coils inside the SG2 unit; they are not the real physically inputs or outputs that
can be wired to any external devices, switches, sensors, etc. The number of Auxiliary Relays M is 63. Since auxiliary
relays are internal elements within the CPU, they can be programmed as digital inputs (contacts) or digital outputs
(coils). In the first rung of this example, auxiliary relay M01 is being used as an output coil and will energize when
input I02 turns on. In the second rung auxiliary relay M01 is being used as an input and when energized, will turn on
outputs Q02 and Q03.
※ The state of auxiliary relays “M01~M3F” will be kept when the smart powers down if “M Keep” is active. “M
Keep” can be set by the two ways below.
Special Auxiliary Relays: M31~M3F
Code Signification Description
M31 User program upstart flag Outputting ON during the first scanning period; and used as
normal auxiliary relay at other scan period.
M32 1second blinking output 0.5s ON, 0.5s OFF
M33 Summer/Winter output Summer time turn ON, winter time turn OFF, used as normal
auxiliary relay.
M34 AT01 flag Output ON when the first channel of SG2-4PT is error
M35 AT02 flag Output ON when the second channel of SG2-4PT is error
M36 AT03 flag Output ON when the third channel of SG2-4PT is error
M37 AT04 flag Output ON when the fourth channel of SG2-4PT is error
M38 RS485 received flag Output ON when the RS485 port has received data.
M39 RS232 received flag Output ON when the RS232 port has received data.
M3A~M3C Reserved
M3D Received flag
M3E Error flag
M3F Time out flag
MODBUS function using
(MU instruction)
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