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Maxiflex P3 PAC User Manual
29
-© Omniflex
UMM126XR18.pdf
5.4 Automatic I/O Scanning
When an I/O module is installed into the system, it will be detected by the CPU in seconds
and then automatically scanned according to its module type. No special configuration is
required for this to occur.
If a User Program is running on the P3 CPU, then the I/O module scanning is synchronised
with the user program scan. If no User Program is running on the P3 CPU, then the I/O is
scanned every 10ms.
Input status information is automatically read from the Input modules and stored in the CPU’s
Dynamic Data area of the DIT Table, and output status information is automatically read from
Dynamic Data area of the DIT Table and written to the relevant output modules.
The layout of the input and output data in the CPU’s DIT is designed to minimise the number
of polls required from a supervisory system to read/write data to the CPU, by grouping
together like types of data.
It is not necessary to have a User Program installed in the P3 CPU for the I/O data to be
accessible by a SCADA/DCS system connected to one of the network ports. User Programs
are only required if you wish to perform some local control or internal data manipulation.