Communication Problems; Preventing Data Loss - Intermec EasyCoder 4420 User Manual

Chapter 4 — Troubleshooting the Printer

Communication Problems

Communications Problems
Symptom
Printer does not
communicate with the host.

Preventing Data Loss

44
If the printer is not receiving downloaded data, try the solutions in the
following table.
Possible Causes
Serial port is incorrectly configured.
Damaged or incorrect I/O cable.
Several problems can cause data loss or communications problems on the
printer. Data loss can result in printing errors or missing field data.
The printer is a serial ASCII device. It communicates with the host
through an ASCII serial communications I/O port. Hardware
handshaking involves the use of a hardware wire. Software handshaking
involves a two-way datalink between the devices. The two devices
communicate with each other without losing data through the use of
handshaking. The printer sends both forms of handshaking simultaneously
when the printer's input buffer is full. Any loss of data can cause printing
errors or missing data.
Hardware handshaking uses pins 11 or 20 of the RS-232 interface to
control data flow. When the printer is using Intermec Standard protocol,
it holds pins 11 and 20 high when it is ready to receive data. The printer
holds the pins low when it is in one of the following conditions:
• Buffer full
• Ribbon fault
• No label stock
• Label at strip pin
The printer uses XON/XOFF protocol for software handshaking. When
the input buffer is full, the printer transmits an XOFF character. This
character alerts the host to the fact that the printer buffer is full and cannot
receive any more data. When the printer is ready to receive more data, it
sends the XON character.
EasyCoder 4420 and 4440 Bar Code Label Printer User's Manual
Solution
Make sure the printer's serial port settings
match those of the host. Print a software test
configuration label as explained in "Using
Test and Service Mode Procedures" in
Chapter 6 to check the serial port settings.
Check the connections at both ends or
replace the cable. See Appendix C for cable
information.