Citizen CLP-621, Technical Manual

Page: 62 / 217

2-4. Interface
CLP-621 & CLP-631
2-50
(3) Protocol
XON/XOFF system:
Controlled with the data transmission request signal X-ON (11H) code and the data
transmission stop request signal X-OFF (13H) code.
The conditions for the X-ON code output are as follows:
•
When the printer is turned from off-line to on-line.
• When the remaining of receive buffer is 1024 bytes or more after sending X-OFF code.
The conditions for the X-OFF code output are as follows:
• When the remainder of receive buffer is 128 bytes or less.
• When the printer is turned from on-line to off-line.
- When the media end is detected.
- When a printer error occurs.
X-ON code sending
X-OFF code sending
16K bytes
1024 bytes
128 bytes
Received data
0 16K
READY/BUSY System:
DTR signal is controlled with READY ("High")/BUSY ("Low") level.
DTR turns to "High (Ready)" in the following conditions:
• When the printer is in on-line mode, and
• When the remaining buffer is 128 bytes or more.
(After DTR becomes "High", DTR retains "High" until the remaining buffer becomes 1024
bytes or less.)
DTR turns to "Low (Busy)" in the following conditions:
• When the printer is in off-line mode.
• When the remaining buffer is less than 128 bytes.
(After DTR becomes "Low", DTR retains "Low" until the remaining buffer becomes 1024 bytes
or more.)