Xon/Xoff Protocol (Software And Hardware Flow Control - Intermec EasyCoder 4420 User Manual

EasyCoder 4420/4440 Bar Code Label Printer User's Manual
The table below shows printer status conditions in descending order of priority:
Printer Status
Buffer already full
Ribbon fault
No label stock
Buffer now full
Printhead hot
Offline (paused)
Label at strip pin
Skipping
Printing
Ready/Online
Note: Do not confuse the Buffer now full <DC3> status with the XON/XOFF
characters <DC1> and <DC3>.
When the printer returns Buffer now full (<DC3>) status, it accepts the currently
received message block. At this time, the printer can accept short messages to allow
parsing of immediate commands such as Reset (<DLE>) or Cancel batch printing
(<EM>). However, if the printer responds with a <GS> to any message block, the
buffer is already full and it discards the entire message block.

XON/XOFF Protocol (Software and Hardware Flow Control)

XON/XOFF protocol uses the ASCII characters <DC1> (XON) and <DC3> (XOFF) to
start and stop the flow of data from the host to the printer. The printer does not restrict
the message length for XON/XOFF protocol. That is, the printer processes information
as it is being downloaded and stops when there is no more information.
<STX> and <ETX> are optional characters. However, if you send an STX, the printer
ignores all other characters until you send an ETX.
Intermec provides two versions of the XON/XOFF protocol. The Intermec version of
XON/XOFF has the printer respond to each message with its current status. The other
version conforms to generally accepted industry standards, which include no end-of-
message response being sent to the host other than XOFF. In addition, a DC3 is sent to
the host if the printer is offline or if media fault occurs. An XON is sent on power up.
C-4
Character
GS
US
EM
DC3
SI
DC3
FS
DC1
DC1
DC1