Mitsubishi Electric MELSEC Q Series User Manual page 262

Receiving side program(CPU No.2)
260
Processing flow
(The numbers from 1) through 9)
represent the execution sequence.)
3) Data are read out from the No.1 module's auto
refresh area into the internal buffer.
4) The No.2 module detects the data set
complete bit (M0) ON.
5) Received data processing is performed.
6) The received data processing complete bit
(area refreshed to No.1 module's M32) is
turned ON.
8) The No.1 module's data set complete bit (M0)
OFF is confirmed.
9) The received data processing complete bit
(area refreshed to No.1 module's M32) is
turned OFF.