Chapter 6 High-speed Link Service
6-15
6.6 High Speed Link at Redundant system
6.6.1 In case of redundant network
When configuration redundant NET, station number and IP address of A-Side and B-side
can be set without restriction. Namely, they can use same station number (IP address) or
different station number because their networks operate respectively. There is no restriction.
[Fig 6.6.1] Redundant network configuration
(1) In case XGR is transmission mode and XGK(I) is reception mode
1) Publication of sequence number
When sending the data at XGR, The first 1 word should publish the sequence
number (SEQ_NO), this sequence number increases by 1 every scan.
2) User data
The data to send actually is set other parts except the first 1 word. Since communication
module of MASTER and STANDBY always execute same service at XGR system, the
reception side should determine which data to get. And when there is error in one side, the
reception part needs program to get the data of another side and not to get the data of one in
error. The reception part can receive the correct data by receiving the data of updated
sequence number.
3) Input data setting of reception side
Reception part take the data of updated sequence number as input data regardless of A-Side
or B-Side and memories the sequence number. Generally, scan time of Standby
communication module is slower than that of Master communication module with amount of
1 scan. So reception part takes the data of Master side as input data and memorizes the
sequence number at that time. Though there is data from Standby side, reception part
ignores that data considering not updated sequence number.
If communication of one side is not available because of line error, the data having the not
updated sequence number is not taken as input. So the user can take advantage of
redundant system.
