Rs-232 Serial Interface Error Handling - Printronix P9212 Setup Manual

with an End of Text (ETX) signal. When the printer receives the ETX, it will
acknowledge the ETX, thereby acknowledging it has received the entire
block of data.
DTR (Data Terminal Ready), RC (Reverse Channel), or RTS (Request to
Send) — Control signals from the printer to the host computer. (Subject to
configuration.) Configurations include: always true, always false, true if
on-line and buffer not full, and true if off-line or buffer almost full. In the
factory default condition, when the printer is off-line or when its buffer is
almost full, these signals are false. When the printer is ready to receive data,
they are true.
This protocol sends no characters to the host; instead, it uses (hardware)
control signals for flow control and other host interface requirements.

RS-232 Serial Interface Error Handling

Parity Error Handling — Parity error checking is a configuration option
selected from the control panel.
With odd or even parity checking selected, a character with a parity error is
replaced with a question mark (?) character. If a parity error is detected and
the ACK/NAK protocol is selected, a NAK character (hex 15) is transmitted
to the host.
When parity checking is not selected ("NONE" on the control panel), parity
errors are ignored and the characters are printed as received.
Framing Error Handling — Framing error checking is always in effect for
the serial interface.
When a framing error occurs, an exclamation point (!) is printed. If 20
successive errors are received, a line feed is added which forces printing to
occur.
Overrun Error Handling — Overrun error checking is always in effect for
the serial interface.
When a data overrun error occurs, an asterisk (*) is printed. If 20 successive
errors are received, a line feed is added which forces printing to occur.
4–12 Printer Interfaces