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GFK-3003AA
Operational Note
STOP and RUN Mode
Transition Priority
Suspend IO Function
Block does not
Suspend EGD
Uploaded Controller
Supplemental Files
lose date and time
CPU Parameters Reset
to Default Values After
Replacing CPU Module
in PME
OPC UA Sessions,
Subscriptions, &
Variables
Description
The PACSystems CPU receives requests to change between a stop and run mode from
many different sources. These include (but are not limited to) PAC Machine Edition, HMIs,
the user application, and the RUN/STOP switch. Since there are many potential sources for
a mode change request, it is possible to receive a new mode change request while another
is already in progress. When this scenario occurs, the CPU evaluates the priority of the new
mode change request with the mode change that is in progress. If the new mode change
request has an equal or higher priority than the one already in progress, the CPU
transitions to the new mode instead of the one in progress. If, however, the new mode
change request has a lower priority than the one in progress, the new mode request is
discarded and the CPU completes the mode change that is in progress. The sweep mode
priorities are (listed from highest to lowest priority) STOP HALT, STOP FAULT, STOP, and
RUN. (NOTE: The IO ENABLED/DISABLED state is not part of the mode priority evaluation.)
For example, a CPU is in RUN IO ENABLED mode, and a Service Request 13 function block
is executed to place the CPU into STOP IO DISABLED mode. Before the transition to STOP
IO DISABLED is completed, the RUN/STOP switch is changed from RUN IO ENABLED to
RUN IO DISABLED. In this case, the CPU ignores the new request from the RUN/STOP
switch to go to RUN IO DISABLED mode because it is already processing a request to go to
STOP IO DISABLED mode, and STOP mode has a higher priority than RUN mode.
In an S90-70 the SUSPEND_IO function block suspends EGD in addition to IO Scan.
In PACSystems controllers the SUSPEND IO only suspends IO Scan.
Controller Supplemental Files uploaded from the CPU are time-stamped as 8/1/1980 at
12:08 AM regardless of PC or PLC time.
When replacing CPU modules in PAC Machine Edition, some parameters may be reset to
default values. After replacing a CPU module, it is recommended that all parameters are
evaluated for application compatibility including the Controller Communication Window
Mode, Controller Communications Window Timer, Backplane Communication Window Mode,
and Backplane Communications Window Timer.
PACSystems OPC UA servers support up to five concurrent sessions with up to ten
concurrent variable subscriptions and up to 12,500 variables. The subscription limit is
shared across all available sessions.
May 2023
32
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