Table of Contents
Advertisement
Triggers and Queues
Loading and
Unloading Queues
In run mode, the DL20 waits for commands from the host. These commands
can:
Trigger a message display
Contain variable display data
To get a better idea of how the DL20 works, you must understand the
concept of a queue. A queue is simply an ordered pile of data. Information
can be put in or taken out of the queue. Information is always taken out in
the same order that it is put in, (i.e. first-in first-out). There are two queues:
One queue holds message numbers
The other queue holds variable data
The DL20 queues up data and message numbers. It empties the message
number queue as fast as it can. A message requires a certain amount of time
to display. An entry is pulled from the data queue each time a control V or
control X is found in a message. Control V or control X is imbedded in a
message in the edit mode. Control V or control X designates "display data
value here". Control V appears as
Control X appears as
(down arrow) when editing a message.
To better understand how the queues operate, refer to this example:
Assume message 2, is "Boiler pressure is
This message is printed along with actual variable data from the host.
Loading Data Queue
First, you must load up the data queue with the variable data. Since the first
control V (up arrow) is the pressure reading, this is the first data that should
be sent followed by the temperature. The data queue will look like this:
First entry:
775
Second entry:
451
Loading Message Trigger Queue
Assume that the message queue is empty. To get the message to display, you
must load the message queue with the message number 2. When this is done,
the message queue will look like this.
First entry:
2
The message is displayed immediately if there are no messages in the queue,
or after any previously-triggered messages have been displayed.
Chapter 5
Run Mode
(up arrow) when editing a message.
PSI, temperature is
degrees".
5–3
Advertisement
Chapters
Table of Contents
