Mitsubishi Electric MELSEC iQ-F Reference page 20

Error code
Error code
(hexadecimal)
100
Error code other than 100
2 FX5 ETHERNET FB
18
2.5 M+FX5UCPU-EN_SLMP_DeviceRead_IP
Description
The setting of i_uDevicePoints (number of device points) is
out of the range.
The set number of device points is out of the range from 1 to
960 (when the 0th bit of the sub command is 0) or out of the
range from 1 to 3972 (when the 0th bit of the sub command is
1).
Same as the error code caused by the SLMP frame sending
(SP.SLMPSND) instruction.
Action
After reviewing the setting, re-execute the FB.
Refer to the MELSEC iQ-F FX5 User's Manual (Ethernet
Communication)