Rockwell Automation 2755 AdaptaScan Software - Manual (Page 150)

10–13
Publication 2755-838
Message Addressing
Message Data is formatted the same as messages sent through the
serial port. When setting up the DeviceNet scanner for addressing
message data, use the following table.
Description Word # Byte # ➀➁
Number of Characters (LSB)
2
2
Number of Characters (MSB)
2
3
First Message Character
(Beginning of Message)
3
4
Other Message Characters
from left to right
3
5 !
Last Message Character
(End of Message) 3+ N where N is the number of characters in
the message.
➀ Bytes #0 and #1 (word 1) are reserved for Discrete I/O. See Page 9–14.
➁ Poll Rx Size = 4 + (# of Characters in string).
Message data is addressed and sent to other DeviceNet devices
through a DeviceNet scanner (Catalog No. 1771-SDN or
1747-SDN). To configure the scanner, you will need to provide the
size of the message data (see page 10–11), the beginning byte and bit
number of the message and the destination of the message data.
Message Flow Control (Handshaking)
DeviceNet Input #8 and Output #16 control the transmission of bar
code messages when using DeviceNet master-slave. Refer to
DeviceNet I/O in Chapter 9. Message flow control (handshaking)
lets the controller know that data is available and keeps the Reader
from sending out messages faster than they can be received. Your
controller logic program must initiate transfers of the message data
and set the DeviceNet Input #8 (Send Next Data) for message flow
control.
New Data
Is indicated by changing the state of Discrete Output #16 of the
DeviceNet I/O. A change of state (0
$1) indicates that message data
is new.
Send Next Data
By changing the state of Discrete Input #8 of the DeviceNet I/O, the
PLC/SLC program control indicates the controller is ready to receive
the next message.
Note: The Application Guide (Publication 2755-6.8) included with
this manual contains an application note for using DeviceNet Master
/ Slave communications.