www.irf.com

7

IRPLDIM2a

Upon entry into the program after setup the microcontroller is held in a loop. While in this loop the microcontroller

is checking for errors, plus it is polling the communications circuitry for incoming data. If valid data is received, it

is filtered to determine if the address matches the defined address for the ballast, if the group matches the defined

group memberships, or if the data is a broadcast command. Also, the type of command is filtered into two basic

choices, standard or special. Once filtered, the program immediately vectors to the appropriate command and

executes. All of the commands are divided into four general categories including arc power control commands,

configuration commands, query commands, and special commands. Within each category the commands are

divided again according to related functions.

The arc power control commands are the most

commonly used in a functioning lighting system.

Within any of these commands appropriate sig-

nals are sent to the ballast controller to adjust

light level via pulse width modulation. This in-

cludes scene level selections. Also many of the

commands in this group select the shutdown bit,

depending on the definition of the command.

Configuration commands are used to setup the

ballast. Examples of such settings include set-

ting minimum and maximum lighting thresholds,

fade times and rates, groups, and scene levels.

Generally data is stored in an EEPROM storage

area where it is maintained regardless of the

power conditions.

Query commands are used to get feedback from

the ballast. All of the settings can be queried.

Even more useful, the status of the ballast is avail-

able. Information about fading, the lamp, general

faults, and power is available through the appro-

priate query command.

Special commands are unique. These com-

mands are immune to addresses; thus all bal-

lasts on the

Digitally Addressable Lighting Interface respond

to a special command. All the functions for find-

ing new ballasts or ballasts that have no ad-

dresses are available. Uploading information to

the ballast, typically settings, is also available in

the special command set.

Fig. 6 Program Flow