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7-7Interfaces
Data T
erminal R
eady (DTR)
- Control signal from the printer. Subject to configuration.
RS-232 Serial Interface Protocols
The following serial interface protocol characters are available. The protocol can be confiĆ
gured
from the control panel to meet host interface requirements.
X-ON/X-OFF - The printer transmits an X-ON character (hex 11) when entering the on
line
state or when the buffer is almost empty.
The printer transmits an X-OFF character (hex
13)
when entering the off line state or when the buffer is almost full.
DTR (Data Terminal Ready) - Control signal from the printer. (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. When the printer is off line, or when its buffer is almost full, DTR
is
toggled. When the printer is ready to receive data, DTR is toggled back.
ETX/ACK
- W
ith ETX/A
CK protocol selected, the
printer interface operates in a block struc
Ć
tured
mode. The host sends a block of data in
response to an A
CK character (hex 06) sent from
the
printer. The host marks the end of the block of data with an ETX character (hex 03). When
the printer recognizes the ETX character, the printer prints the data block and checks the
space available in the buffer. If space is available for the next block of data, the printer sends
ACK to the host. If space is not available, the printer withholds ACK until sufficient space is
available.
ACK/NAK - With ACK/NAK protocol selected, the printer responds as described for ETX/
ACK
protocol except the printer monitors the received data for parity error. If a
parity error is
detected, a NAK character is transmitted to the host upon receipt of the ETX character. The
host
is expected to repeat the data transmission.
RS-232 INTERFACE ERROR - With an odd or even parity check in effect, an erroneous
character
shall be replaced with
a question mark (?). If a parity error is detected, a NAK char
Ć
acter
(hex 15) is transmitted to the host when the A
CK/NAK protocol is selected. When parity
is not checked, parity errors are ignored and the characters are printed as received. Parity
checking is a configuration option selected from the control panel. When a framing error ocĆ
curs,
an exclamation point (!) will be printed. When a data overrun
error occurs, an asterisk (*)
will
be printed. After 20 successive errors have been received, a line feed is added which forces
printing
to occur.
RTS (Request To Send) - Control signal from the printer. Subject to configuration. Refer to
DTR
above for detailed configuration actions.
Reverse Channel (RC) - Control signal from the printer. Subject to configuration. Refer to
DTR above for specific configuration actions. (Reverse Channel is not an official RS-232C
signal;
it is included for compatibility with earlier
Printronix
products.)
RS-232 Serial Interface Configuration
The printer is configured at the factory according to the specified interface as shown in the
Configuration
chapter. However, the interface configuration parameters can be changed. The
following configuration parameters can be verified or changed as necessary to meet specific
application
requirements: