Common Memory - Mitsubishi Electric FR-F720-55K Instruction Manual

CYCLIC TRANSMISSION
6.1

Common memory

Concept of common memory is stated below.
(1) The common memory is used as a shared memory between nodes which perform cyclic transmission.
(2) The common memory has two areas which are "common memory area 1" and "common memory area
2".
Common memory area 1 is I/O data area. Common memory area 2 is the control information area.
Two different areas can be assigned to each node.
(3) When the area each node sends exceed the transmission size (1024 byte) by one frame, data is
transmitted by multiple frames.
(4) When receiving data which are divided into multiple frames as (3), common memory is not updated until
all frames sent from one node are received. Synchronism per node unit is guaranteed.
(5) Entire network has an area of 8k bit (0.5k word) + 8k word = 8.5k word.
The maximum send data capacity per one node is 8.5k word. (Note that one word is 2 byte.)
15
2
Common memory area 1
=Input/output data area
Common memory area 2
=Control information area
42
0
2
0.5k Word
8k Word
Common memory area
8.5k Word