Scanner Operation; At Power Up; In Run Mode; When Changing From Run Mode - Allen-Bradley 1747-SN User Manual

Scanner Operation

Below is a description of the scanner's operation at power up, run
mode, and when changing from run mode to program or test mode.

At Power Up

At power up, the the scanner's communication LED (green LED) is
off until the SLC is changed to Run or Test mode.

In Run Mode

During normal scanner operation (SLC in Run mode), the scanner's
LEDs illuminate as shown below:
SCANNER
COMM FAULT

When Changing From Run Mode

When the SLC processor is changed from Run mode, to Program or
Test mode the following occurs:
scanner's COMM LED remains green.
the scanner continues to read its input devices and send output
data to its RIO adapters.
the scanner instructs adapters to either clear all outputs or hold
them in their last state (depending on their configuration). Refer
to the user manual included with each RIO device for specific
information relating to the Hold Last State setting.
Important:
If you are using Block Transfer (BT) functionality, BTs
may not function on adapters in Hold Last State
settings. Refer to each device's user manual for
information on BTs and Hold Last State settings.
Installation and Wiring
FAULT LED is off.
COMM LED is green.
Publication 1747 6.6 - July 1996
3–7