Printronix ProLine 5 Series Manual page 158

character. An XOFF character is sent when the number of empty bytes
in the buffer is less than or equal to 25 percent of the buffer size. If the
host keeps sending data after an XOFF is sent, the printer firmware will
continue to send an XOFF for every 16 characters received. When
cleared, the printer will resume receiving data (XON). The data does
not have any End of Text codes; XON / XOFF is a non–block protocol.
ETX / ACK: End of Text / Acknowledge. The host controls the flow of
communication to the printer by sending a block of data and ending the
block with an End of Text (ETX) signal. When the printer receives the
ETX signal, it will acknowledge the ETX, thereby acknowledging it has
received the entire block of data.
ACK / NAK: ACK means acknowledge; the device acknowledges it has
accepted a transmission. NAK means a negative acknowledge; the
device did not receive the transmission.
DTR: The printer controls the data flow by sending this hardware signal
to the host. If there is enough room in the printer buffer, the printer will
send a high signal; if the buffer is full the printer will send a low signal.
DTR tells the host if it is safe to send more data. (If the host sends data
during an unsafe condition, data will be lost.) DTR is not available when
RS–422 is selected.
SERIES 1 1 CHAR: The printer controls the flow of communication from
the host by turning the transmission on and off using response
characters sent to the host. If the number of valid bytes in the buffer
reaches 75 percent of the buffer size, the online or offline and buffer full
response character is sent. If the buffer is completely full, an online or
offline buffer full response is sent every time a character is sent from
the host. Whenever the printer state changes to online or offline, the
appropriate response character is sent. If the idle response option is
enabled, the printer will send a response character every two seconds
while the number of valid bytes in the buffer is less than 75 percent of
the buffer size. If a poll character is received (configurable from the Poll
Character xx Hex option on the front panel from 0 through FF hex), the
printer will send a response character n milliseconds later (configurable
Configuration Menus 4–105