Mitsubishi Electric MELSEC iQ-R16MTCPU Programming Manual page 45

Special relay/special register
The special relays and special register relating to the inter-module synchronization function are shown below. Refer to the
following for details on special relays and special registers.
• Special relay(Page 426 Special Relays)
• Special register(Page 431 Special Registers)
Device Number Name
Special relay SM480 Motion operation cycle over flag
SM488 Module synchronization error detection
Special register SD480 Motion CPU operation cycle over counter No.
Inter-module synchronization function in Multiple CPU configuration
■Operating specifications
Refer to relationship between fixed scan communication and inter-module synchronization for the motion operation cycle
relationship when fixed scan communication and inter-module synchronization are combined. (Page 47 Relationship
between fixed scan communication and inter-module synchronization)
The data flow when fixed scan communication and the inter-module synchronization function are combined and
communicating with the PLC CPU is as follows.
• When the Multiple CPU synchronous interrupt function and inter-module synchronization function are combined (PLC CPU
 Motion CPU)
Two inter-module synchronization cycles are required for data acquired by the PLC CPU by the time it reaches the Motion
CPU via the CPU buffer memory (fixed scan communication area). When synchronizing output between CPUs, use a
function block for the inter-module synchronization function with a PLC CPU, and program taking into account the
difference in output timing (two cycles) between the PLC CPU control module and Motion CPU control module.
• When the Multiple CPU synchronous interrupt function and inter-module synchronization function are combined (Motion
CPU  PLC CPU)
One inter-module synchronization cycle is required for data acquired by the Motion CPU by the time it reaches the PLC
CPU via the CPU buffer memory (fixed scan communication area). If synchronizing output between CPUs, adjust the
number of Motion SFC fixed-cycle event task consecutive transitions for the Motion CPU, and program taking into account
the difference in output timing (one cycle) between the PLC CPU control module and Motion CPU control module.
■Module access from other CPU
Even if the following settings are set in GX Works3, inputs (X) and outputs (Y) cannot be read from modules subject to the
inter-module synchronization function. Reading from the buffer memory is possible by direct access with a module access
device (U\G), FROM instruction, etc.
• When set to "import" at the [System Parameter]  [Multiple CPU Setting]  "Other PLC Control Module Setting"  "I/O
Setting Outside Group".
■Aligning the inter-module synchronization function start timing at all CPUs, all stations
Specify the following settings in GX Works3.
• Set each module in [System Parameter]  [Synchronization Setting within the Modules]  "Select Synchronous Target
Unit between Unit" to "Synchronize".
• Set all CPUs in [System Parameter]  [Multiple CPU Setting]  "Operation Mode Setting"  "Synchronous Startup
Setting" to "Synchronize".
1.3 Data Communication Between CPU Modules in the Multiple CPU System
1 MULTIPLE CPU SYSTEM
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