12-5
12.3.3 Communication Protocols
1) General Description of DTR Mode Operation
This mode is set when the DIPSW #1-3 are turned ON. (The ex-factory setting)
This mode performs communication while handshaking with the DTR signals. In the operations to receive
printer data, this mode controls the DTR signals by confirming the BUSY signal. A SPACE indicates that the
printer is ready to receive data; conversely, a “mark” indicates that the printer cannot receive data.
RXD
RXD
DTR
DTR
Print Operation
Data Data Data
Buffer Full Buffer Empty
Power ON
OFF LINE ON LINE
Power ON
Print Operation
Paper Out Signal
Paper Out
Press ONLINE Switch
After Setting Paper
b. When There is No Paper
a.
If there is no printer error after turning ON the power, the DTR signal line is set to a SPACE. When the host
computer confirms that the DTR signal line is a SPACE, it sends the data text to the RXD signal line. The
printer sets the DTR signal line to a “Mark” after the empty area of the data buffer reaches a maximum of 256
bytes. When the host computer confirms that the DTR signal line is a Mark, it stops the transmission of data
text to the printer buffer, but at this point as well, the printer is still capable of receiving data, up to the
amount of empty space in the data buffer. If the host computer ignores the DTR signal and transmits data, all
data exceeding the amount of space in the data buffer is simply discarded. The printer sets the DTR signal
line to SPACE again when the amount of empty space in the data buffer increased because of the printing
and the data in the buffer is a maximum of 256 bytes.
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