Rockwell Automation 1799-DASCII DeviceNet Serial Interface - Manual (Page 29)

DeviceNet Serial Interface Module 29
Publication 1799-IN012B-EN-P - July 2008
Transmit String Data Type Formats (parameter 22)
This is the format of the data sent from the 1799-DASCII module - array,
short_string, or string - to the DeviceNet master. These are shown in the following
sections. Which one you pick depends on the application and modifies the format
of the data field. To change the string format, use parameter 22.
Set Up and Use the TX Byte Swap Mode (parameter 23)
This option is helpful if the 1799-DASCII module is connected to a DeviceNet
scanner that organizes the data string characters into data type elements that are
larger than 1 byte each. An example is an Allen-Bradley PLC, such as the SLC 500
controller. In such cases, the bytes of the data in the master's memory organization
can be reversed from the order in which they are sent or received on the DeviceNet
network and the serial link to the ASCII device. This may cause anomalies in some
cases.
Identify Scanner I/O Transmit Size (parameter 24)
The 1799-DASCII module automatically calculates the number of bytes it expects
from the DeviceNet master. Its value is determined by a combination of the
incoming data and the options selected. Parameter 24 is a read-only value that
defines the size of the DeviceNet message sent to the 1799-DASCII module from the
master.
Consume Data DeviceNet Format - Short_String Data Type
Byte 1 Byte 2 Byte 3 Byte 4 Byte 5-X (128 bytes max)
Rx ID Byte (Handshake
mode only) Transaction ID
Byte Reserved Length ASCII data (including optional
<terminator>.
Consume Data DeviceNet Assembly Format - String Data Type
Byte 1 Byte 2 Byte 3 Byte 4 Byte 5-X (max 128 bytes)
Rx ID Byte (Handshake
mode only) Transaction ID
Byte Length (low byte) Length (high byte) ASCII data (including optional
<terminator>.
IMPORTANT
Set the scanner’s produce size value to this number of bytes.