Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 286)

Chapter 15
Using Communication Protocols
15–2
Responder (Slave) Communication
Responder products can only reply to other products. These devices are not
capable of initiating an exchange of data; they only reply to requests made
from initiator products. The Series A and B MicroLogix 1000 controllers are
in this class.
The MSG is an output instruction that allows the controller to initiate an
exchange of data with other devices. The relationship with the other devices
can be either peer-to-peer communication or master-to-slave communication.
The type of communication required by a particular application determines
the programming configuration requirements of the MSG instruction.
Entering Parameters
When entering a message instruction, the following parameters need to be entered:
•
Read/Write – read indicates that the local processor (processor in which
the instruction is located) is receiving data; write indicates that the
processor is sending data.
•
Target Device – identifies the type of command used to establish
communication. The target device can be a MicroLogix 1000 controller or
SLC family processor using SLC commands, or a common interface file by
selecting the CIF (Common Interface File) format. Valid options are:
– SLC500/ML1000 – Allows communication between a
MicroLogix 1000 controller and any other MicroLogix 1000 controller
or SLC 500 family processor.
– CIF – (Common Interface File) Allows communication between a
MicroLogix 1000 controller and a non-MicroLogix 1000/SLC 500
device. The CIF data is automatically delivered to integer file 9 in
SLC 500 processors or integer file 7 in MicroLogix 1000 controllers.
The CIF protocol is also used for PLC-2 type messages.
•
Control Block Address – an integer file address that you select. It
consists of seven integer words, containing the status bits, target file
address, and other data associated with the MSG instruction.
•
Control Block Length – fixed at seven elements. This field cannot be
altered.
•
Target Node – the node address of the target device. Valid entries are
0–254 for DF1; 0–31 for DH-485.
•
Local Address – the address of the local device.
•
Target Address – If SLC500/ML1000 is selected as the target device, a
target address must be entered.
•
Target Offset – If CIF is selected as the target device, you must enter a
value for the offset into the CIF.
•
Message Length – specifies the length of the message instruction in
elements. 1-word elements are limited to 1–41; 3-word elements are
limited to 1–13.
Important: When running a MicroLogix 1000 program on an SLC 5/03 or
SLC 5/04 processor, the MSG control block length increases from
7 to 14 words. If you plan to run a MicroLogix 1000 program
with one of these processors, make sure that the program has at
least 7 unused words following each MSG control block.
MSG
READ/WRITE MESSAGE
Read/Write
WRITE
Target Device SLC500/ML1000
Control Block N7:0
Control Block Length 7
Execution Times (
µ
sec) when:
True False
180
➀
48
Ladder representation:
➀
This only includes the amount of time
needed to set up the operation requested. It
does not include the time it takes to service the
actual communication, as this time varies with
each network configuration. As an example,
144ms is the actual communication service
time for the following configuration: 3 nodes
on DH-485 (2=MicroLogix 1000 programmable
controllers and 1=PLC-500 A.I. Series
t
programming software), running at 19.2K
baud, with 2 words per transfer.
(EN)
(DN)
(ER)
Message Instruction (MSG)