Rockwell Automation 1734-485ASC POINT I/O ASCII User Manual - Manual (Page 52)

Publication 1734-UM009B-EN-P - July 2003
2-26 Configuring Your ASCII Module
Transmitting Serial Data
The length of the string sent determines the use of a delimiter in
transmitting data to a serial device from the ASCII module.
· If the string length is zero (as dynamically defined by the third
and fourth bytes in the message header), or if the data type is
Array:
The ASCII module receives data sent from the DeviceNet master
and uses the delimiter to determine how much data is sent to
the serial device. The ASCII module will compute the length and
then store this as the new length in the string attribute. (This will
not show up if the data type is array, you will just see the string
truncated, and the length will be in the background.)
· If the string length > 0 or the data type is String or Short_String:
The ASCII module receives data sent from the DeviceNet master
ignoring any embedded terminator. It will store the number of
characters defined in Max_Number_of_Transmit_Chars, or the
total sent by the master, whichever is less.
The ASCII module will send the information immediately in Transmit
Immediate mode. You can always cause the data to be transmitted by
changing the TX ID.
Setting Up the Scanner I/O Transmit Size
The ASCII module automatically calculates the number of bytes it will
receive from the DeviceNet master. Its value is determined by a
combination of the incoming data and the options you have selected.
Parameter 23 defines the size of the DeviceNet message to be sent to
the ASCII module from the master and should be set as the Tx size in
your Scanner’s I/O set-up.
IMPORTANT
You must set your scanner’s Tx (transmit) value to
this number of bytes. Remember to upload this data
from the ASCII module to current information or put
your RSNetWorx for DeviceNet into Monitor Mode.