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About Communications
The 7421 printer supports both serial and parallel
communications. Using the parallel interface with an IEEE 1284
parallel interface cable (Part No. 590124) provides the best
performance.
Your printer has the following hardware and software
requirements:
• The host computer must use the American Standard Code for
Information Exchange (ASCII) for data communications.
• A serial port or a parallel port must be available on the host if
you are connecting directly to the printer.
• The host must support the RS-232 or data communications
interface.
For information on configuring the host computer, port
concentrator, or network controller, see the reference manual for
the controlling device.
Serial Communication Protocols
Communication protocols are important because they determine
the transmission standards for communications between the
printer and the host. The printer and the host must use the same
protocol and parameters to communicate properly. The printer
supports the flow control and block transfer protocols described
in the next sections. All of these protocols are point-to-point.
Application programs and/or ROM BIOS determine which
protocols your computer can support. For more detailed
information, refer to the Intermec Data Communications Reference
Manual (Part No. 044737).
Intermec Printer Standard Protocol
Intermec Printer Standard Protocol is a half-duplex protocol. All
data transmission to the printer consists of status enquiry (ENQ),
status dump (VT), or message blocks. Each message block starts
with the Start of Text (STX) characters and ends with the End of
Text (ETX) characters. Each message block must be 255
characters or less, including the STX and ETX characters.