Historical Event Recording - Allen-Bradley A-B QUALITY DL20 Series User Manual

Historical Event Recording

Historical Event Recording allows you to designate messages as stackable
messages. These messages are triggered, displayed, and stored. Later, all the
messages in this stack can be printed on demand. Any variable data
contained within a message, such as time of day, is also stored.
Use Historical Event Recording feature when you want a printed record of all
the error messages or a report generated from your application. Even though
the DL20 already supports printing of messages, it requires a printer hooked
up permanently because the messages are printed immediately after they are
triggered. With the Historical Event Recording feature, you can connect a
printer, print the contents of the Historical Event Recorder, and disconnect
the printer. An advantage is that a printer is not required for every DL20. If
you have more than one DL20, one printer can be shared among them.
Using the Historical Event Recording feature involves three steps.
1. Select messages that you want stacked using the message editor.
2. Messages are triggered in the usual way in the run mode.
3. Print out the contents of the Historical Events Recorder at any time.
The STACK MSG attribute designates the messages that are to be stored in
the Historical Event Recorder. All messages in the DL20 can be designated
as stackable messages. You only want to stack only the most important
messages, or the alarm messages. See Chapter 4 for setting message
attributes.
The stack is limited to 3K of the DL20's unused memory. Typing control F
while in the message editor displays the amount of available memory. Each
stacked message requires 3 bytes of stack memory; each variable in the
message requires 4 bytes of stack memory; and the time-of-day string
requires 26 bytes of stack memory. As you can see, a stack with 3,000 byte
capacity can hold quite a few message triggers. This stack is stored in
battery-backed RAM memory and is retained even when the power is off. It
will not be retained if the run mode is exited. To print the stack messages
use special message #5.
Special messages #5, #6, #7, #15 and #16 are directly associated with
Historical Event Recording. These special messages were described earlier
in this chapter.
Chapter 5
Run Mode
5–17