•Transmit timing of the X-on signal

The X-on signal is transmitted when the power is first turned on, and when the vacant area in the buffer is greater than the preset value of the buffer recovery timing. Refer to Table 12 for information on flag set/reset conditions.

Figure 3. X-on/X-off timing

X-ONX-OFF X-OFFX-ON

POWER ON

Buffer

 

Buffer

Buffer capacity

 

capacity: 512

capacity

specified with

 

or 16

bytes

0 byte

DIP switches

 

 

 

 

3-2 and 3-3.

DTR protocol

This interface card also provides for DTR handshaking protocol using either RS-232D, RS-422A, 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 flag set level, the DTR sets the status flag to prohibit further data entry. This flag is output through the DTR (pin No. 20) under RS-232D signal levels, through the TRA and TRB (pin No. 11, 13) under RS-422A signal levels, and through the TTY-TXD (pin No. 17) under Current-Loop levels.

18