Printronix T8000 Administrator's Manual page 170

This option determines how data bit 8 is treated from the host.
Disable
Enable
Factory Default
IMPORTANT
The Data Polarity parameter must be set to match the data polarity of your
host computer.
Standard
Inverted
Factory Default
The Response Polarity parameter must be set to match the response
polarity of your host computer.
Standard
Inverted
Factory Default
170
Host IO > Centronics > Data Bit 8
When the host PI line is enabled, data bit 8 internally
indicates PI line status. To use the PI line, disable data
bit 8, and enable the Host PI configuration option
(under the PI Ignored option).
The PI line is not passed directly from host to printer;
all 8 bits are used for data bits, and characters in the
hex 80-FF range can be accessed.
Enable
Data bit 8 is interpreted as either data bit 8 or PI
signal, but never both. When enabled as data bit 8,
data bit 8 has priority over the PI signal, and all
data above hex 7F is used to access character
data and not to interpret PI line data.
Conversely, when data bit 8 is disabled and the PI
signal is used, data bit 8 of the data is reserved for
use as the PI function, and you cannot access
characters in the hex 80-FF range. Therefore, to
access characters in the hex 80-FF range, data bit
8 must be enabled.
Host IO > Centronics > Data Polarity
Does not expect the host computer to invert the data.
Expects the data received on the data lines from the
host computer to be inverted. Ones become zeros and
vice versa.
Standard
Host IO > Centronics > Resp. Polarity
Does not invert the response signal.
Inverts the response signal sent to the host computer.
Standard