Appendix C— Communications Reference
96
EasyCoder 4420 and 4440 Bar Code Label Printer User’s Manual
Polling Mode D
Polling Mode D is a block transfer protocol that transmits data in blocks
of up to 255 characters, including protocol overhead. For Polling Mode D,
the host/concentrator is responsible for asking the printer for data it might
have (polling) and requesting to send data to the printer (selecting). LRC
characters frame the blocks for additional data integrity. Use Polling Mode
D for point-to-point networks that connect the printer to an Intermec
port concentrator (RS-232 or RS-422 are acceptable).
This protocol is the default setting for the 4420 and 4440 printer. Return
the protocol setting to Polling Mode D by setting the printer DIP switches
to the factory default settings (9600, E, 7, 1) or by sending down the Test
and Service mode command D.
Multi-Drop Protocol
Use Multi-Drop protocol to connect up to 32 devices to an Intermec
controller on a four-wire RS-485 (two twisted pair). This protocol is
similar to Polling Mode D except each device has a unique address (POL
and SEL character). You must use an RS-485, which is automatically
enabled when you enable Multi-Drop. Be sure to specify a unique address
for the printer and verify that the baud rate is between 2400 and 19200.
Hardware Protocol
The printer uses Ready/Busy and DTR (data terminal ready) of the RS-
232C interface to indicate the printer’s status. You can configure
Ready/Busy and DTR independent of each other and independent of the
software protocol you select for the serial port. You can set each pin to one
of these three settings: default, high, and Ready/Busy.
When you set the pin to high, the printer will be ready to accept data
anytime.
When you set the pin to Ready/Busy, the pin is high when the printer
status is ready. The pin is held low when the printer is in one of these
conditions:
• Offline
• Buffer full
• No label stock
• Ribbon fault
• Label at strip pin
If you set the printer to XON/XOFF protocol, the XON and XOFF
characters will not be transmitted back to the host.