Warm Start / Cold Start; Table 17 Scan Rates Per Inputs Configured - Honeywell UMC800 Installation And User Manual

Operation

Warm Start / Cold Start

Warm Start / Cold Start
Housekeeping and diagnostic routines are performed during power up sequence of the controller and prior
to the controller microprocessor starting normal scan processing. During this sequence all logic outputs are
OFF and all analog outputs are held to their zero output states.
After this activity, the controller may perform either a cold start or a warm start of the controller
configuration. Warm start is the default mode of start-up.
Warm start
A warm start begins the scan cycle with all dynamic data retained from the previous valid scan. A warm
start occurs after a power up sequence with the configuration database integrity in RAM being verified. A
warm start is initiated when the controller mode is set from Offline mode to run.
Cold start
A cold start initializes all functions to their default initialized states. If default output values are defined,
these values are used as the starting values for restart of the controller.
A cold start is performed when:
A file download is performed through the control builder program.
The mode is set from PROGRAM to RUN through the SET MODE display of the operator interface.
Setting the controller manual mode switch from PROGRAM to OFFLINE or RUN. In this case, the
controller always performs a cold start.
The configuration database in RAM is found to be invalid during power up sequence.
Scan rates
The analog input scan rate is a function of the total number of configured inputs in the controller as well as
the number and type of configured function blocks. Table 17 shows the fastest scan rate time for the
number of analog input cards, although the actual scan rate will be the slower of either the analog input rate
or the function block execution rate. Analog outputs are always scanned at the analog input scan rate, as
well as function blocks and digital I/Os that are not configured for fast logic. Function blocks and digital
I/Os that are configured for fast logic are updated every 100 milliseconds.
58

Table 17 Scan rates per inputs configured

Number of analog input cards
1
2
3
4
5
6
7
UMC800 Controller Installation and User Guide
Time to complete one full
scan
(in milliseconds)
333
500
700
900
1100
1300
1500
Release F
4/01