User manual

Transferring Data with the I/O Scanner
33002479 06 07/2008 207
The Device
Control Block
The Device Control Block lets you disable any scanned device by setting a bit
associated with that device to 1. The I/O scanner closes the connection and sets the
Health Bit to 0 (unhealthy state).
To enable the Device Control Block select the checkbox in the I/O Scanner
configuration dialog (item 2 in the illustration above).
It is possible (but meaningless) to access %MW attached to the outputs because
they will not be transmitted to the device.
Note: To enable the Device Control Block, you must have:
z Unity Pro at V2.0 or higher
z An NOE 771 01 or NOE 771 11at version 3.5 or higher
z A 140 CPU 651x0 at version 2.0 or higher
If you attempt to enable the Device Control Block with an earlier version of the
firmware, the I/O scanning service is disabled.
If the checkbox is not selected, the I/O scanner service is enabled, and you cannot
disable the I/O scanning of individual devices.
Disabling I/O scanning with the Device Control Block is equivalent to ending
communication between the scanner and the device. Therefore:
z the fallback positions are applied to the inputs by the scanner
z communication with the device is stopped
z all the entries in the IN and OUT tables are still transferred between the CPU
and the scanner on each scan
As a consequence of the last point above, if you modify a %MWi attached to an
input, this %MWi is overwritten by the values coming from the I/O scanner in the
next scan (with either 0 or the last input value).