Rockwell Automation 1747-ASB Remote I/O Adapter - Manual (Page 142)

Publication 1747-UM006B-EN-P - June 2003
B-2 Differences Between the 1747-ASB Module and the 1771-ASB Series C Module
Hold Last State Operation
(page 4-15) When the hold last state mode is selected, the 1771-ASB module holds
discrete outputs in their last state if:
•
an error occurs
•
RIO communications are lost
•
the 1771-ASB module is inhibited
•
the 1771-ASB module receives reset, adapter decide commands
from the scanner
When the hold last state mode is selected the 1747-ASB module holds
discrete outputs in their last state if:
•
RIO communications are lost
•
the 1747-ASB module is inhibited
•
the 1771-ASB module receives reset, adapter decide commands
from the scanner
The 1747-ASB module always clears discrete outputs if:
•
an I/O module fault occurs
•
a 1747-ASB error occurs
•
a remote expansion chassis loses power
Remote Expansion Chassis
(page 3-1) The 1771-ASB module does not support expansion chassis. It allows
up to 16 physical slots in one 1771 chassis.
The 1747-ASB module can control up to three chassis; a remote
chassis and two remote expansion chassis. If power to any remote
expansion chassis is lost, a 1747-ASB error occurs and all discrete
outputs are cleared, regardless of the hold last state switch setting.
When power to the remote expansion chassis is restored, the ASB
module automatically resumes operation as if the ASB module's
power was cycled.
ATTENTION
!
When the discrete outputs are being held in their last
state by the 1747-ASB module, the following
information concerning the specialty modules must
be considered:
The specialty I/O modules operate as if they are
being controlled by an SLC processor in the run
mode. Refer to the specialty I/O module's user
manual to determine the response to this condition.
The specialty I/O modules inputs are read by the
ASB module. However, the specialty I/O module's
outputs are not modified by the ASB module.