Rockwell Automation 1734-485ASC POINT I/O ASCII User Manual - Manual (Page 23)

Publication 1734-UM009B-EN-P - July 2003
Installing the ASCII Module 1-13
The transmit and receive sizes of the I/O connection are automatically
computed for you by the ASCII module. You must set the maximum
RX and TX sizes first and then choose apply. Upload the data to the
ASCII module by clicking Upload. The scanner’s I/O connection TX
field should be set to the value of "Consume Assembly Size"
parameter 23.
The RX size of the scanner should be set to the value of "Produce
Assembly Size" parameter 13. If you are in the COS I/O connection
and do not wish to transmit data out of the ASCII module, you may
set the scanner’s TX size to 0. This will only work with the COS/cyclic
connection. You will see the best results if you do not allocate the poll
and COS connections at the same time (you will conserve bandwidth).
The best selection in regards to bandwidth conservation is the COS
connection.
Setting Up the Connection Timer (EPR)
EPR stands for Expected Packet Rate. This is the timer value that the
ASCII module uses for the cyclic and polled connection. This is also
the value it uses in the connections to calculate the time the device
should wait before signaling a timeout. If you have a scanner or
scanning software, you must configure it with the EPR that you want
the ASCII module to be scanned with.
The scanner configures the EPR in the ASCII module at the
beginning of communications. Consult your scanner’s manuals on
how to configure the EPR.
IMPORTANT
Remember to re-map the data (if necessary) after you
set the sizes, because many configuration tools will
automatically unmap your data when you change the
connection sizes. If you are not using such a
software package, it is probably not necessary to set
up the transmit and receive sizes.
TIP
EPR is automatically set via RSNetWorx for
DeviceNet. However, if you need to set up the EPR
manually, perform a set (Service 10
hex
) on the
connection class (Class 5
hex
) attribute 9. The polled
connection uses instance 2, where as the COS and
cyclic connections use instance 4. This must be done
after allocating the connection.