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13.6 Data Mapping Configuration (Scan List Entry)
Update Type
This field specifies the direction and what triggers the transfer of data between the OCS and
target device for a mapping entry.
Polled Read
On every transaction scan, a read-only target device register(s) transaction occurs.
Polled Read/Write
On every transaction scan, a read target device register transaction occurs unless a local
register value has changed. The write transaction only updates those local registers that have
changed in value. If several non-consecutive local registers (contained in a single mapping
entry) change value between transaction scans, it takes several consecutive transaction scans
to write each changed register.
When the OCS is placed in RUN mode, the initial action for this mapping type is a read target
register transaction. This transaction initializes the local (OCS) register(s) to match that of the
remote device register(s). Thereafter, any change to the corresponding OCS register(s)
triggers a write operation to the remote device.