Rockwell Automation 1336T ControlNet Frn1.02 Rev 1.5 - Manual (Page 44)

4–2 Using Unscheduled Messaging
Publication 1336 FORCE–5.18 ––March, 1999
The message instruction is used to read and write a block of data to
another station on the ControlNet link. The following is a
description of the message instruction field data. Refer to the
example program at the end of this chapter for a message instruction
example.
This function: Specifies:
Communication
Command
Whether the MSG instruction performs a
PLC5 TYPED READ to read data from
the drive or a PLC 5 TYPED WRITE to
write data to the drive.
PLC5 Data Table
Address
The data file address where data is stored.
• If the MSG operation is a write, this
address is the starting word of the source
file for data sent to the PLC
Communications Adapter Board.
• If the MSG operation is a read, this
address is the starting word of the
destination file for data returned from the
PLC Communications Adapter Board.
Size In Elements
The number of elements to be transferred.
Note that:
• For a Read Parameter function, each
element is one word. Therefore, when
reading 10 parameter values, the field
needs to be a length of 10 elements.
• For a Read Parameter Full, each element
is 20 words long. Therefore, a Read Full
function of 6 parameters requires an
entry of 120 elements.
• For N40, the size must be 64 words.
Local/Remote
Local indicates the message is sent to a
device on the local CN link. For this
application, this field is always local.
Local Node Address
The local station address on the CN link.
This is defined through the DIP switch
(U3) on the PLC Communications
Adapter Board.
Destination Data
Table Address
The starting address represents the type of
service requested at the PLC
Communications Adapter Board
destination file. Refer to the CN
Command Set section for more
information.
Message Instruction