The Windows printer management has been designed for page-based printers: laser printers and shared network printers. The printer driver does not print anything on the printer until the page is full; it then prints the page. This is the preferred printing method (when printers are shared on a network), because it minimizes the likelihood of conflict of data when more than one operator uses the print facility at the same time.
However, this method is inappropriate when logging
alarms or keyboard commands. If you send alarm logging to this type
of printer, CitectSCADA
flushes the data to the printer when the current activity
completes, or when the [DEVICE]FlushTime parameter has been exceeded
(it defaults to 10 seconds). If, for example, you have one alarm
occurring each minute, each alarm is printed on a new page (because
the default flush time is less than the alarm frequency).
You can bypass the Windows print management by
writing the output to a file. Set the device type to ASCII_DEV and
specify the file name as lpt1.dos,
lpt2.dos or lpt3.dos (depending on the port to which your
printer is connected). The printer needs to be either on a local
port, or a captured network printer. When you log to this device,
the data is printed immediately on the printer with no extra form
feeds.
For correct logging operation, reserve one printer to be your logging printer. This printer has to be a local printer, not on the network server. You can then send any other non-logging printouts, (for example, reports) to a shared network or local printer.
See Also