Rockwell Automation 1747-DSN DISTRIBUTED I/O SCANNER - Manual (Page 33)

Chapter 4
Operation and Troubleshooting
4–3
CAUTION:
Make sure that you clearly understand the
implications of disabling a scanner module slot before
utilizing this feature.
!
The scanner slot disable operation is the same in the 7 I/O and 30 I/O block
configurations.
When the scanner’s slot is disabled by the SLC processor, the SLC proces-
sor outputs will no longer be sent to the scanner (or to the I/O blocks) and
the scanner inputs (or I/O block inputs) will no longer be sent to the SLC
processor. The SLC processor input image and the outputs sent to the I/O
blocks by the scanner will be held in the state that they were when the slot
was disabled. The scanner will continue to collect inputs from the I/O
blocks even though they are not sent to the SLC processor, and changes can
be made to the SLC processor output image even though they will not be
sent to the scanner (or I/O blocks).
If power on the SLC Rack is cycled when the slot is disabled, the scanner
will no longer communicate on the DIO Link and the I/O block outputs will
be reset to 0. The SLC processor input image will reflect the state of the
scanner inputs when the slot was originally disabled.
When the slot is re–enabled, the inputs from the scanner to the SLC proces-
sor will reflect the current state of the I/O block inputs and the current state
of the SLC processor output image will be sent to the scanner (and the I/O
blocks).
When communication between the scanner and I/O block(s) is lost:
•
the bits in the Communication Status Word for the non–communicating
I/O block(s) are reset to 0
•
the I/O block(s) input image found in the scanner and SLC processor
remains at the last state read from the I/O blocks before communications
was lost.
•
the entire SLC processor output image continues to be transferred to the
scanner, however, outputs will not be sent to non–communicating I/O
blocks.
When communications is restored:
•
the corresponding bits in the Communication Status Word are set to 1
•
the current information in the SLC processor and scanner output image is
sent to the I/O block(s)
•
the current state of the I/O block(s) inputs is sent to the scanner and SLC
processor.
To determine the operation of the I/O blocks when communications is lost,
refer to the I/O block User’s Manual.
Scanner Slot Disable
Operation
Loss of Communications