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EasyCoder 3400e Bar Code Label Printer User’s Manual
HelvC
NugFont
C39
C-4
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 the printer discards the entire message block.
XON/XOFF Protocol (Software and Hardware Flow Control)
The XON/XOFF protocol stops the host from sending data when the printer buffer fills
up and starts the host again when the buffer empties. When you select this protocol, you
concurrently enable software and hardware flow control. Software flow control uses the
ASCII characters <DC1> (XON) and <DC3> (XOFF) to start and stop the flow of data
from the host to the printer. Hardware flow control uses pin 11 or pin 20 (internally
connected together) on the printer’s serial port to indicate “Ready” or “Busy” for data
flow control. As with Standard protocol, <STX> and <ETX> enclose data. Status
responses conform to the table above except that <DC2> is substituted for <DC1> and
<DC4> is substituted for <DC3>.
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. There is no restriction on the number of characters that can be sent
down at a time. <STX> and <ETX> are optional characters.
Pin 11/20 reports “Ready” and a <DC1> (XON) is transmitted when the printer finishes
reloading at power-up. Pin 11/20 reports “Busy” when the printer’s input buffer fills
with 768 bytes of data. If the host ignores pin 11/20 and continues to transmit data, the
printer transmits a <DC3> (XOFF) after receiving 15 additional characters. The printer
continues to transmit a <DC3> after every 15 characters received if the host continues
to transmit data. Data integrity is not guaranteed if this happens.
Pin 11/20 becomes “Ready” when the printer has transferred all the data from the input
buffer. If the printer receives a <DC3>, it transmits a <DC1> (XON) and the host may
resume transmission. When you switch the printer offline, pin 11/20 becomes “Busy”
and it transmits a <DC3>. When you switch the printer online (and the input buffer is
empty), pin 11/20 becomes “Ready” and it transmits a DC1.