Printronix L5020 - Manual (Page 71)

Dataproducts Parameters
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Data Bit 8
Values: Enable (default) or Disable.
Normally, this parameter is enabled. It allows access to the
extended ASCII character set.
Paper Inst (Instruction) Line
Values: Enable or Disable (default).
The Paper Instruction line (PI line) controls paper motion. It is
dependent on your host computer.
Data Polarity
Values: Standard (default) or Inverted.
This parameter must be set to match the Data signal polarity of
your host computer.
There are normally seven or eight data bits that define each ASCII
character sent from the host computer to the printer. The bits are
usually high-true.
Strobe Polarity
Values: Standard (default) or Inverted.
This parameter must be set to match the Data Strobe signal polarity
of your host computer.
When the host computer sends a data strobe signal, it is indicating
that it has placed data on the data bus and that the data is valid
(i.e., enough time has elapsed for the data lines to stabilize). The
data strobe signal forces the printer to read the data lines into its
input buffer.
Data Req (Request) Polarity
Values: Standard (default) or Inverted.
This parameter must be set to match the Data Request signal
polarity of your host computer.
Data Request is a high-true signal sent by the printer requesting
data from the host.