Rockwell Automation 284A ArmorStart with ArmorPoint Backplane - Getting Started - Manual (Page 19)

Publication 284A-QS001C-EN-P - July 2006
19
Theory of Operation
It is possible to connect an ArmorStart product to the Point I/O based subnet
of the ArmorPoint I/O system. This allows the ArmorStart to be connected
to EtherNetIP and ControlNet, along with the original DeviceNet. The
easiest way to program these ArmorStarts is to use RSNetWorx for
DeviceNet software, bridging through the appropriate network. This
ladder logic has been developed as an alternate method of configuration.
Once the appropriate device configuration is done to a User Defined
Structure in the ladder logic file, a bit will need to be turned on in the logic
to trigger a system wide read of the system. This system wide read, goes out
and reads certain attributes of every parameter of every ArmorStart in the
system and stores the information into a large data array. The first attribute
is a flag word that tells the ladder logic if the parameter is read only. If the
read only bit is set, then the ladder logic will skip the additional attribute
reads and will go to the next parameter. If the parameter is writable, then the
logic will read the size, min. allowed value, max. allowed value, the
parameter name, help string and the raw data of each parameter. These
attributes are stored in the data array for use later when the configuration is
written to each ArmorStart. The logic requires that a system wide read
function be completed prior to a system wide write function being
requested.
Note: A system wide read function should be done anytime that a new
ArmorStart is added to the system or an ArmorStart is updated with
a more recent version. This assures that the data array in the logic
matches the total system.
Once a system wide read is done, the raw data of the individual parameters
in the data array can be modified and a system wide write function activated
from a bit in the ladder logic. Only parameters that changed will be written
to the ArmorStart devices, and after a write is done the parameter is read
back and stored in the data array for comparison. If the write and reread
value do not match, an Error Report is generated.
If an error occurs for any reason, during a system wide read or write, an
error report will be logged, containing the device and parameter it occurred
on. Also the status and extended status of the message block is logged in
case the error originated there.