23.12.2012 Views

Safety Considerations Guide for Trident v2 Systems - TUV ...

Safety Considerations Guide for Trident v2 Systems - TUV ...

Safety Considerations Guide for Trident v2 Systems - TUV ...

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Data Transfer Time<br />

Data Transfer Time 65<br />

In a Peer-to-Peer application, data transfer time includes the time required to initiate a send<br />

operation, send the message over the network, and have the message read by the receiving<br />

node. Additional time (at least two scans) is required <strong>for</strong> a sending node to get an<br />

acknowledgment from the MPs that the message has been acted on.<br />

These time periods are a function of the following parameters of the sending and receiving<br />

controllers:<br />

• Scan time<br />

• Configuration size<br />

• Number of bytes <strong>for</strong> aliased variables<br />

• Number of SEND function blocks, RECEIVE function blocks, printing function blocks,<br />

and Modbus master function blocks<br />

• Number of controllers (nodes) on the Peer-to-Peer network<br />

Send function blocks require multiple scans to transfer data from the sending controller to the<br />

receiving controller. The number of send operations initiated in a scan is limited to 5. The<br />

number of pending send operations is limited to 10.<br />

Estimating Memory <strong>for</strong> Peer-to-Peer Data Transfer Time<br />

This procedure explains how to estimate memory <strong>for</strong> Peer-to-Peer data transfer time between a<br />

pair of Triconex controllers (nodes). The more memory allocated <strong>for</strong> aliased points the slower<br />

the transfer time.<br />

Procedure<br />

1 In the TriStation 1131 software, on the sending controller, expand the Controller tree,<br />

and double-click Configuration. On the Configuration tree, click Memory Allocation.<br />

2 Find the bytes allocated <strong>for</strong> BOOL, DINT, and REAL points by doing this:<br />

• On the Configuration tree, click Memory Points, Input Points, or Output Points.<br />

Double-click the graphic <strong>for</strong> the point type.<br />

• Add the number of bytes allocated <strong>for</strong> all BOOL input, output, and aliased memory<br />

points. Enter the number on step 1 of the following worksheet. Enter the number <strong>for</strong><br />

DINT and REAL points on step 1.<br />

3 On the receiving controller, get the BOOL, DINT, and REAL points and enter the<br />

numbers on step 3 of the Data Transfer Time worksheet.<br />

Estimating the Data Transfer Time<br />

The basic <strong>for</strong>mula <strong>for</strong> estimating the data transfer time is as follows:<br />

• Data transfer time in milliseconds = 2 * (larger of TS or SS) + 2 * (larger of TR or SR)<br />

<strong>Safety</strong> <strong>Considerations</strong> <strong>Guide</strong> <strong>for</strong> <strong>Trident</strong> <strong>v2</strong> <strong>Systems</strong>

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!