Mitsubishi Electric RD77GF8 User Manual page 27

Differences from link refresh
Item
Number of steps
*1
Processing speed
Cyclic data integrity assurance
*1 For actual values, refer to the following.
MELSEC iQ-R Programming Manual (CPU Module Instructions, Standard Functions/Function Blocks)
Shortening the link refresh time and transmission delay time
■Shortening the link refresh time
Remove infrequently used link devices from the link refresh range, and directly read or write the corresponding data using link
direct devices. This reduces the number of the link refresh points to the CPU module, resulting in a shorter link refresh time.
(Page 21 Link refresh)
■Shortening the transmission delay time
Because the link direct device allows direct reading or writing of data to the link devices of the Simple Motion module at the
time of the instruction execution, the transmission delay time can be shortened.
Link refresh is executed in END processing of the sequence scan of the CPU module.
Precautions
■Cyclic data integrity assurance
Direct access to link devices does not provide station-based block data assurance. Use 32-bit data assurance, or if cyclic data
of more than 32 bits needs to be assured, use interlock programs. (Page 26 Cyclic data integrity assurance)
■Mounting multiple modules of the same network No.
When multiple Simple Motion modules of the same network No. are mounted, the target of direct access is the module which
has the smallest slot No. in the base unit.
■Link direct device in a multiple CPU system
In a multiple CPU system, link direct devices cannot be used for the CC-Link IE Controller Network-equipped module
controlled by another CPU module.
Access method
Link refresh
1 step
High speed
Available
Direct access
2 steps
Low speed
Not available
1 FUNCTIONS
1.3 Cyclic Transmission
1
25