SUMMARY: This document provides detailed information on the operation of the mL170 serial interface.

RS-232C Interface Signals

Serial Menu

The following options can be set in the Serial Menu:

Note: Defaults are indicated in bold.

Note: The following parameters are fixed:

Buffer

The buffer size is set under Config Menu >> I/O Buffers and can be set to Auto (default), 32K, 64K, 128K, or 256K bytes. The low trip point is 255 bytes and the high trip point is 255 bytes from the top of the buffer.

Pacing

Different types of protocols are used for the RS-232C serial interface, depending on the computer manufacturer. These protocols prevent the print data receive buffer from overflowing because 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 the buffer status, as follows:

X-ON/X-OFF

With this protocol, the XOFF code (hexadecimal 13) is transmitted from the printer when less than 255 bytes of buffer space remains. The XON code (hexadecimal 11) is transmitted when less than 255 bytes of data remains in the buffer. Normal data processing cannot be guaranteed if data is transmitted to the printer when insufficient buffer space is available after the XOFF code has been transmitted. When the printer is first turned on, the DTR signal is set high (ready) and an XON 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.

DTR protocol

The DTR signal is set off (low) when the buffer empties to the low trip point of 255 bytes of data. When the printer is placed offline, the DTR signal is set off (low). Transmission must stop within 255 bytes after the DTR signal is set off (low). The validity of data cannot be guaranteed if data exceeding the buffer capacity is transmitted regardless of the DTR signal.

Buffer-full recovery timing

Data transmission is suspended while the DTR signal is set off (low), but printing continues. When the buffer empty area exceeds 255 bytes, the DTR signal is set on (high) indicating that the printer is ready to accept data.

Robust XON

When Robust XON is set to on, the printer is online, and the serial interface is ready, the XON code (hexadecimal 11) is transmitted once per second.

Cable Connections

The mL170 uses a modem style cable. Typical connections are as follows:

• 25 pin connector on host side:

• 9 pin connector on host side:

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