Rice Lake Star SP298 Series Programmers Manual - Manual (Page 17)

14
Data protocol
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Outline of DTR/DSR mode operations
This communication mode is set when dip switches 1 to 6 are set at ON.
The DTR signal shakes hands with the DSR signal (DSR signal: ESC/POS
mode only) and performs communications. The DTR signal is assumed as the
BUSY signal and then the control for the printer’s data receiving operations
are carreied out, and a “space” means that the printer is to receive the data, and
a “mark” means that the printer is not to receive the data.
The DTR signal line is set a “space” when the power supply is switched on and
no error occurs with the printer. The host confirms that the DTR signal line is
set at “space”, and then transmits the text data to the RXD signal line.
The printer sets the DTR signal line at “mark” when the empty area in the data
buffer is less that the prescribed number of bytes (*1: nearly full buffer
condition.) The host confirms that the DTR signal line is set at “mark” and
suspends text data transmission, but it is possible for the printer to continue
receiving data for the amount of space remaining in the data buffer’s empty area
at this point. If the DTR signal is ignored and data transmitted, the data that
exceeds the amount of space available in the empty area will be discarded. The
empty area in the data buffer will increase as printing is carried out, and the
DTR signal line will be set at “space” if the amount of empty space in the data
buffer is more than the prescribed number of bytes (*2: near empty condition.)
In addition to this, the host will confirm that receiving is possible (DSR signal
= “space”) and transmit the data only when memory switches 4 and 5 are set
at 0 during printer status transmission in the ESC/POS mode’s DTR/DSR
communication mode. (With the exception of certain status transmission
commands. Also, dip switches 1 to 9 must be at OFF when the DSR signal is
confirmed.)
*1 Refer to the nearly full buffer conditions for details on nearly full buffer conditions.
*2 Refer to the nearly empty buffer conditions for details on nearly empty buffer
conditions.
RXD
DTR
Data Data Data
Buffer full Buffer empty
Printing
Power ON