3.3 Multi-CPU Functions
Slave CPU Synchronization
3-108
Scan Overhead Guidelines When Using Sub CPU Synchronization
This section provides guidelines for the scan overhead times for the sizes of CPU interface registers for
high-speed and low-speed scans.
CPU Interface Registers for High-speed Scan
This section describes the data transfer timing for CPU interface registers for the high-speed scans.
If the time set for the high-speed scan in the CPU Unit is shorter than the overhead time, a scan exceeded
error will occur and SW00044 (H Scan Exceeded Count) will be incremented. If that occurs, adjust the
high-speed scan set value based on the above table.
The following figure illustrates high-speed scan processing.
CPU Interface Registers for Low-speed Scan
The following table gives approximate times for the low-speed scan overhead that is required for different
sizes of CPU interface registers for the low-speed scan.
If the time set for the low-speed scan in the CPU Unit is shorter than the overhead time, a scan exceeded
error will occur and SW00046 (L Scan Exceeded Count) will be incremented. If that occurs, adjust the
low-speed scan set value based on the above table.
The following figure illustrates low-speed scan processing.
Slave CPU Synchronization
Refer to the following manual for details on slave CPU synchronization.
MP3000 Series Motion Control User’s Manual
(Manual No.: SIEP C880725 11)
Item
I/O Size
512 Words
1,024 Words
2,048 Words
Guideline Times for CPU Interface
Overhead
25
μ
s
50
μ
s
100
μ
s
Item
I/O Size
512 Words
1,024 Words
2,048 Words
Guideline Times for CPU Interface Overhead
100
μ
s
200
μ
s
300
μ
s
CPU interface
DWG.H
SVC processing
(status)
SVC processing
(motion processing)
Current high-speed scan time
Overhead time
High-speed scan set value
CPU interface
High-speed scan
CPU interface
DWG.L
Current low-speed scan time
Overhead time
Low-speed scan set value
CPU interface
Low-speed scan