Mitsubishi Electric MELSEC Q Series User Manual page 143

If the operation of a CPU is halted by a stop error, a "MULTI CPU DOWN (error code : 7000)" stop error will occur at the CPU
on which the error was detected.
Depending on the timing of error detection, a "MULTI CPU DOWN" error may be detected in a CPU of "MULTI CPU DOWN"
status, not the first CPU on which a stop error occurs.
For example, if a stop error occurs in CPU No.2 and CPU No.3 is halted as a direct consequence of this, CPU No.1 may be
halted because of the stop error on CPU No.3 depending on the timing of error detection.
Because of this, CPU No. different from the one of initial error CPU may be stored in the error data's common information
category.
To restore the system, remove the error cause on the CPU that is stopped by an error other than "MULTI CPU DOWN".
In Figure 3.37, the cause of the CPU No.2 error that did not cause the "MULTI CPU DOWN" error is to be removed.
3 - 38
1) Stop with "OPERATION ERROR".
CPU 0 1 2 3 4
1 2 3 1 2 3
2) Stop occurs with stop error detection of CPU No. 2.
("MULTI CPU DOWN" occurs.)
3) Stop may occur with stop error detection of CPU No. 3
depending on the error detection timing.
("MULTI CPU DOWN" occurs.)
Figure 3.36 Detection of stop error
Figure 3.37 Error display by PLC diagnosis
Slot number
Control CPU setting