Description of Operation
Section
3-2
87
3-2-2
Details of Hot Start, Cold Start and Stop State
There are two modes in which running of the Loop Control Unit is started: hot
start and cold start.
Assuming DIP switch pin 2 is OFF, the default mode for the Loop Control Unit
is a hot start when the power to the PC is turned ON or the Loop Control Unit
is restarted.
By a hot start, operation is started continued at the state that was active
before the stop occurred. This mode is effective when a short power OFF
such as an instantaneous power interruption has occurred.
By a cold start, operation is started after all internal operation memory is
initialized. (PID is reset to Manual.) This mode is effective when running is
started after a long power OFF.
The following table describes each of the Loop Control Unit states at a hot
start, cold start or in a stop state.
Start of running
Description
Hot start
Cold start
Run stop
State active before the
unit was stopped is
continued before
running is started.
Operation is started
after contact/analog
I/O values and
internally held values
are cleared to zero.
Running is
stopped with the
state active
before the stop
held.
Set Point
State active before
stop is held.
MV
0%
Control
blocks
Auto/Manual
switching
Manual state
Parameter
State active before
stop is held.
Contact/analog I/O
value
Initialization
1
Control
blocks,
Operation
blocks
Internal hold value
for operation
Initialization
1
Step Ladder Program
State active before
stop is held.
2
STEP01
State active
before stop is
held.
2
Status of Loop
Control Unit
(allocated CIO area)
Execution at each 1s regardless of running state
Data
exchange
with CPU
Unit
Data exchange with
function blocks
Refresh is executed at each running cycle.
Data exchange
stopped
1: Data to be initialized (cleared) at a cold start are the following values
held internally for operations:
Result of previous operation on time function blocks such as the First-
order Lag block or Accumulator blocks
Current measurement values of the Step Ladder Program block such as
the Timer block or Counter block
2: Parameters that are held in memory are all ITEMs and values held
internally for operations