ABOUT THE CONTROLLER'S MEMORY MAP
About the Controller's Memory Map
Like SNAP Ethernet-based brains, a SNAP PAC S-series controller uses a memory mapped system for
storing data and making that data available to other devices on the Ethernet network. This data
includes configuration data, status information about the controller itself, and PAC Control strategy
variable data that may be needed by a peer on the network.
Although SNAP PAC S-series controllers are designed to run PAC Control strategies, you can also
write your own software applications to communicate with the controller's memory map, either
instead of or in addition to using PAC Control. You can use the OptoMMP Communication Toolkit or
the IEEE 1394-based protocol for writing your applications. Both are explained in Opto 22 form 1465,
the OptoMMP Protocol Guide, which also includes complete details of the memory map. Although
this guide is written for I/O units, you can use the same information for a SNAP PAC S-series
controller. Just be aware that many sections do not apply, since the controller's memory map doesn't
include any I/O point or related information.
The SNAP PAC S-series controller's memory map includes only the following areas:
Status Area Read
Communications Port Configuration
Date and Time Configuration
Status Area Write
Using Data for Peer-to-Peer Communication
Scratch Pad areas within the SNAP PAC S-series controller's memory map provide a way for other
devices on the Ethernet network to access data in the controller. For descriptions of the Scratch Pad
areas—bits, integers, floats, and strings—see the PAC Manager User' s Guide. For help in using PAC
Control commands to access Scratch Pad areas, see "I/O Unit—Scratch Pad Commands" in Chapter
10 of the PAC Control User's Guide.
If you are not using PAC Control but writing your own software applications to access the Scratch Pad
areas, see the OptoMMP Protocol Guide. This guide is written for I/O units, but much of the same
information on programming applies to SNAP PAC S-series and other Ethernet-based Opto 22
controllers. The Scratch Pad areas of the memory map are described in the programming guide's
appendix; the SNAP PAC S-series controller's Scratch Pad areas are identical to the Scratch Pad areas
on the SNAP Ultimate brain.
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SNAP PAC S-Series User's Guide
Security Configuration
PPP Configuration
PPP Status
Scratch Pad