The input relay is an internal memory (storage) unit in the PLC corresponding to a external
input point and is used for connecting to the external input switches and receiving external
input signals. The input relay will be driven by the external input signals which make it “0” or
“1". Program designing cannot modify the status of the relay, i.e. it cannot re-write the basic
unit of a relay, nor can it force On/Off of the relay by HPP/WPLSoft.
SA/SX/SC/EH2/SV/EH3/SV2 series MPU can simulate input relay X and force On/Off of the
relay. But the status of the external input points will be updated and disabled, i.e. the external
input signals will not be read into their corresponding memories inside PLC, but only the input
points on the MPU. The input points on the extension modules will still operate normally. There
are no limitations on the times of using contact A and contact B of the input relay. The input
relays without corresponding input signals can only be left unused and cannot be used for
other purposes.
Device indication: X0, X1,…X7, X10, X11,… are indicated as X and numbered in octal
form. The No. of input points are marked on MPU and extension modules.