6 F 3 B 0 3 5 6
2. Scan transmission overview
The Scan transmission method is suitable for real time control data linkage.
In the S20LP, data sending station is rotated cyclically. Each station has common memory for Scan transmission. The size of the common memory is 4096 words. When a station becomes the data sender station, it sends data of prespecified area of the common memory. All other stations receive the data, and store them into their common memory. Therefore, the common memory in each station is totally updated in a transmission cycle.
The common memory is allocated to the Link register (W) in the T2N/T3H. The size of the link register is 2048 words. The link register is a part of common memory. By simply reading/writing data from/to the Link registers, high speed data linkage is achieved.
S20LP
T2N STN
Common
memory
(1)
Send
(2)
Receive
(3)
Receive
T2N’s Link
register
Write
Read
T2N STN
Common
memory
(1)
Receive
(2)
Send
(3)
Receive
T2N’s Link
register
Read
Write
Read
T3H STN
Common
memory
(1)
Receive
(2)
Receive
(3)
Send
T3H’s Link
register
Read
Write
Note 1) The data send block(s) of each station is prespecified by using the
Note 2) Data transfer between common memory and Link registers is executed by T2N/T3H's OS. The transfer direction (read or write) is automatically decided.
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