Illegal Message Trigger Indication; Variable Stack Empty Indication; Printer Handshaking - Allen-Bradley A-B QUALITY DL20 Series User Manual

Chapter 5
Run Mode
Illegal Message
Trigger Indication
Variable Stack
Empty Indication

Printer Handshaking

5–16
An error message is displayed when a non-existing message is triggered.
This feature is selected by responding with a [Y] to the FLAG ERRORS?
prompt in the Set Up Master special function. Then, if an invalid message
trigger is received, the message
is displayed on line one. The message is displayed until a valid message
trigger is received. If the error reporting is not enabled, invalid message
triggers are ignored.
It is possible to signal an error when a control V (which tells the DL20 to
look for a new variable in the queues) is found in a message and there is no
new data in the variable queue. This feature is selected by responding to
the menu prompt as described in Chapter 8 (FLAG ERRORS?).
This is done by displaying characters in place of the variable(s):
If it is a formatted variable, stars are displayed filling the entire field.
If it is a non-formatted variable, a random number of stars (up to 6) are
displayed.
If error reporting is not enabled, random numbers appear as the variables, if
new data is not found in the stack.
Printer handshaking controls the flow of data between a DL20 and a printer.
DL20s use the software XON/XOFF protocol so that the DL20 starts and
stops sending characters as the printer is able to print them. If the printer
sends an XOFF, but does not send an XON while a message is being
displayed, the message remains on the display until it receives three [Esc]s,
an XON character, or special message #2, #3 or #10.
ILLEGAL MSG TRIGGER