Rockwell Automation 1203 Serial Communications Module Series B - Manual (Page 33)

Chapter
3
1203–5.5 September 1995
SCANport Datalink Operation
In this chapter, you will read about SCANport Datalinks.
A Datalink is a type of pointer function used by some SCANport
devices to transfer parameter values to and from the SCANport
device. The Datalink function transfers parameters on a regular
schedule. Reading a parameter using the Datalink function (data
table N41) requires less time than reading a parameter using the
Parameter Value Read data table addresses (data tables N10 – N19 or
N50 – N89) because the module is kept updated on the parameter
value.
SCANport devices that support this function have a group of
parameters for Datalink configuration. These parameters are
identified as Datalink In and Datalink Out parameters. To enable the
Datalink functions, you need to:
1. Set the correct switch to Enable on SW3 of the Serial
Communications Module.
2. Configure the Datalink In and Datalink Out parameters in the
SCANport device.
Each Datalink consists of two 16-bit words of input and two 16-bit
words of output. You can configure each of the two input words to
write to a different destination parameter within the SCANport
device by setting the two Datalink In parameters for that Datalink to
the desired destination parameters. Similarly, you can configure each
of the two output words by setting the two Datalink Out parameters
for that Datalink.
Each Datalink switch on SW3 can enable or disable one Datalink.
•
If a Datalink is enabled, the value of the parameters set into the
Datalink Out parameters is transferred to the Serial
Communications Module and the data sent by the Serial
Communications Module for the Datalink is transferred into the
parameters set into the Datalink In parameters.
•
If a Datalink is not enabled, the data transferred to the SCANport
device for that Datalink is zero and the Serial Communications
Module ignores any data sent by the SCANport device.
If no Datalink In parameter is configured for an input word, that
word is ignored. If no Datalink Out parameter is configured for an
output word, the output word is undefined (usually set to zero).
Chapter Objectives
SCANport Datalinks