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greater than the preset value of the buffer recovery
timing. Refer to Table 5. for buffer recovery timing
information
Figure 3. X-on/x-off timing
DTR protocol
This interface board also provides for DTR handshaking
protocol using either RS-232C or Current Loop signal
levels
Under this system, when the printer is turned on the
DTR enters the SPACE state, meaning that data entry is
enabled. When the rate of data reception is greater than
that of printing, the buffer gradually fills up. once the
vacant area for transmitted bytes drops to 512 or 1
bytes, the DTR sets the status flag to prohibit further.
data entry. This flag is output through the DTR (pin No.
20) under RS-232C signal levels, and through the TTY-
TXD (pin No. 17) under Current Loop levels.
15
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