Printronix T5000 Series, Руководство пользователя

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Chapter 3
SERIAL PORT
Data Protocol
You can select one of the following serial interface protocols to meet the host
interface requirements.
•
XON / XOFF. The printer controls the flow of communication from the host
by turning the transmission on and off. In some situations, such as when
the buffer is full or the timing of signals is too slow or too fast, the printer
will tell the host to stop transmission by sending an XOFF 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 negative acknowledge; the device
did not receive the transmission.
•
Series1 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 hex 0 through FF), the printer will
send a response character n milliseconds later (configurable from the Poll
Character xx MS on the front panel from 0 through 30). This n
milliseconds is called the poll delay. The poll character will be removed
from the input data stream and will not be processed. This may cause
problems with the transmission of binary data (e.g. control codes, bit
image, etc.). If a poll delay is started due to the receipt of a poll character
and another poll character is received, the second poll character has no
effect, and is removed from the input data stream. If a transition (from
buffer full to empty or online to offline) occurs during a poll delay, the new
printer state will be sent at the end of the poll delay.