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Chapter
3
3-1
MMS and Your OSI Coprocessor
This chapter covers how your OSI coprocessor supports MMS services, it
contains the following sections:
The Supported MMS Services
Mapping MMS Data Types onto PLC–5 Controller Data Files
Additional Information on Using Data Types
MMS Object Management
MMS
Security
We assume you are already familiar with MMS and programming PLC–5
controllers. Refer to Chapter 1 if you would like a brief overview of MAP
and MMS.
The following tables list each MMS service that your OSI coprocessor
supports, and a brief description of each service.
Unless otherwise stated, the OSI coprocessor performs all functions
associated with the server side of an MMS service without user
intervention. The OSI coprocessor allows use of the client side of an
MMS service by the execution of instructions in a PLC–5 application
program.
MMS Service: Description: Support:
Initiate Enables communication between the OSI coprocessor and another MMS
device by making a connection with the other device. All MMS
communication (except for the Initiate request and response) must be sent
across an open connection. Note that the PLC-5 controller message
instruction can ask the OSI coprocessor to connect to itself, which enables
the execution of message instructions that perform MMS services within the
local PLC-5 system.
Client and server. To invoke the client side of the Initiate
service, an OPEN command is programmed into the PLC-5
controller. The server side is invoked when the OSI
coprocessor receives an Initiate request.
Conclude Gracefully terminates a connection between the OSI coprocessor and another
MMS device. Upon successful completion of the Conclude service, no further
communication can take place between the OSI coprocessor and the other
MMS device until another connection is opened. This is the preferred service
to terminate a connection.
Client and server. To invoke the client side of the conclude
service, a CLOSE command is programmed into the PLC-5
controller. The server side is invoked when the OSI
coprocessor receives a conclude request.
Abort Abruptly terminates a connection between the OSI coprocessor and another
MMS device. Upon completion of the abort service, no further communication
can take place between the OSI coprocessor and the other MMS device until
another connection is opened. This MMS service should only be used in
extreme conditions.
Client and server. To invoke the client side of the Abort
service, an ABORT command is programmed into the PLC-5
controller. The server side is invoked when the OSI
coprocessor receives an abort request.
Chapter Objectives
The Supported MMS
Services
AB Parts