Safety Considerations Guide for Triconex General ... - ICEWeb

Data Transfer Time 63
Data Transfer Time
In a Peer-to-Peer application, data transfer time includes the time required to initiate a send
operation, send the message over the network, and have the message read by the receiving
node. Additional time (at least two scans) is required for a sending node to get an
acknowledgment from the MPs that the message has been acted on.
These time periods are a function of the following parameters of the sending and receiving
controllers:
• Scan time
• Configuration size
• Number of bytes for aliased variables
• Number of SEND function blocks, RECEIVE function blocks, printing function blocks,
and Modbus master function blocks
• Number of controllers (nodes) on the Peer-to-Peer network
Send function blocks require multiple scans to transfer data from the sending controller to the
receiving controller. The number of send operations initiated in a scan is limited to 5. The
number of pending send operations is limited to 10.
Estimating Memory for Peer-to-Peer Data Transfer Time
This procedure explains how to estimate memory for Peer-to-Peer data transfer time between a
pair of Triconex controllers (nodes). The more memory allocated for aliased points the slower
the transfer time.
Procedure
1 In the TriStation 1131 software, on the sending controller, expand the Controller tree,
and double-click Configuration. On the Configuration tree, click Memory Allocation.
2 Find the bytes allocated for BOOL, DINT, and REAL points by doing this:
• On the Configuration tree, click Memory Points, Input Points, or Output Points.
Double-click the graphic for the point type.
• Add the number of bytes allocated for all BOOL input, output, and aliased memory
points. Enter the number on step 1 of the following worksheet. Enter the number for
DINT and REAL points on step 1.
3 On the receiving controller, get the BOOL, DINT, and REAL points and enter the
numbers on step 3 of the Data Transfer Time worksheet.
Estimating the Data Transfer Time
The basic formula for estimating the data transfer time is as follows:
• Data transfer time in milliseconds = 2 * (larger of TS or SS) + 2 * (larger of TR or SR)
Safety Considerations Guide for Triconex General Purpose v2 Systems