Special Message #9: Clear Queues, Halt Run Mode; Special Message #10: Clear Queues; Special Message #11: Test Display - Allen-Bradley A-B QUALITY DL20 Series User Manual

Special Message #9: Clear Queues, Halt Run Mode

Use special message #9 when dynamic chaining has been selected. Special
message #9 inhibits the unqueuing and display of incoming message triggers.
Message and data queues are also cleared.
Special messages #8 and #9 work together to start and stop message display.
Use these messages when dynamic chaining is enabled. The dynamic
chaining mode is described in more detail later in this chapter. The way
these messages would be used with dynamic chaining is as follows:
1. Trigger special message #9. This causes the display to stop unqueuing
messages and empties the message and data queues.
2. Send other message triggers (up to 20). They are stored in the queue.
3. Trigger special message #8 to begin unqueing and repetitive display of
these messages.
4. Messages are displayed continuously, until special message #9 is
triggered.
5. Trigger special message #9, you will be able to reload the message queue
with new message triggers.
6. The process can be repeated.

Special Message #10: Clear Queues

Special message #10 clears the queues. This special message works exactly
the same as special message #2, except that the display is not cleared. This is
useful when messages are triggered with variable data.
To trigger a message with variable data, your program must send the variable
data followed by the message number. The way some programs are written,
if they are interrupted or switch modes (from run to test, for example) they
may have sent over some variable data but did not trigger the message
associated with it. If a new message with variable data is triggered,
incorrect variable data (intended for the never-triggered message) is
displayed. To ensure that the variables in the messages are in sync with the
message trigger, you can trigger special message #10, send the variable data,
and then trigger the new message. The old message is replaced with the new
message without the display going blank between messages.

Special Message #11: Test Display

Special message #11 tests the display. All the segments of the display as
well as all the segments of any attached slave displays are illuminated. This
feature is useful if your application includes a lamp test button. You can
program the controller to trigger special message #11 when this button is
pressed.
Chapter 5
Run Mode
5–9