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.

Table 17 Scan rates per inputs configured

Number of analog input cards

1

2

3

4

5

6

7

Time to complete one full

scan

(in milliseconds)

333

500

700

900

1100

1300

1500

58

UMC800 Controller Installation and User Guide

Release F

 

 

4/01

Page 66
Image 66
Honeywell UMC800 manual Warm Start / Cold Start, Warm start, Cold start, Scan rates per inputs configured