Description Of Input And Output Signals; Electrical Characteristics - Citizen BD2-1220 User Manual

7.2 Description of Input and Output Signals

(1) RD
This is a serial reception data signal. When a framing error, overrun error or parity error occurs, the data
containing the error is printed as a "?".
(2) DTR
When this signal is Ready, you can write data or commands into the input buffer. If you do so while the
signal is Busy, an overrun error occurs, and the previously written data will be ignored. Data can be written
into the input buffer even during printing. A Busy signal is also issued at the time of power-on, test printing,
on-line communication, and resetting.
(3) TD
As data is received, the remaining capacity of the printer's input buffer decreases. When it becomes less than
128 bytes, a DC3 (13H) (Data reception disable signal) is output to the host computer. On the other hand,
when the remaining capacity of the input buffer increases to 256 or more bytes, a DC1 (11H) (Data reception
enable signal) is output to the host computer. This signal is valid only if communication mode is set to XON/
XOFF.
(4) DSR
When sending status information, if DTR/DSR control is selected, the host computer transfers data to the
control board after checking this signal is a space. If DTR/DSR control is not selected, the host computer
ignores this signal and sends data to the control board. Transmit data is transferred through the TD lines. Note
that, if status information is requested when this signal is at Mark, status information sending is held up until
it is set to Space.
(5) GND
This is a common ground on circuits.

7.3 Electrical Characteristics

RS-232C circuit
Input (RD, DSR)
Output (TD, DTR)
Printer Side
Eqivalent to MAX232
Printer Side
Eqivalent to MAX232
Host Side
Host Side
18
BD2-1220/1221 User's Manual