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5.3.5 Data protocols
The following four protocols are used for the RS-232C serial interface, depending on the computer hardware.
• XON/XOFF or DC1/DC3
• DTR
• RC
These protocols prevent overflow of the print data receive buffer when interface data transmission is faster than
buffer data printing. The printer uses specific character codes or an interface signal for each protocol to inform
the computer of buffer status.
Selecting IBM character set 1 validates the ETX/ACK protocol, regardless of the emulation used.
(1) XON/XOFF or DC1/DC3 protocol
The XOFF (DC3) code (hexadecimal 13) is transmitted from the printer when less than 255
(*1)
bytes remains
in the buffer. The XON (DC1) code (hexadecimal 11) is transmitted when less than 255 bytes of data
remains in the buffer.
*1 This value is 63 bytes when the print buffer is configured for 256 BYTE in setup mode.
Data processing cannot be guaranteed if data is transmitted to the printer but sufficient buffer space is not
available after the XOFF code has been transmitted.
When the printer is first turned on, the DTR signal is set to the space state (ready) and an XON (DC1) code
is transmitted from the printer. When the printer is placed offline, the XOFF code is transmitted even if the
buffer is not full. The XON code is transmitted when the printer is placed online again.
If paper runs out, a NAK code (hexadecimal 15) is sent from the printer.