Explanation Of Input/Output Signals; Error Detection; Data Receiving Control - Citizen BD2-2880 User Manual

7.2 Explanation of Input/Output Signals

(1) RXD
Serial receiving data signal. On occurrence of framing error, overrun error, or parity error, the
data is printed as "?".
(2) DTR
When this signal is READY, write data or a command. When they are written in BUSY, overrun
error is occurred and data is ignored. Data can be written into the input buffer even when the
printer is busy printing. A BUSY also occurs when the printer is powered on, in test print, in
Online mode, or being reset.
(3) TXD
If data remaining in the printer's input buffer is 256 bytes or less, the printer transfers a DC3
(13H: Data Receive Not Ready) signal to the host. If data in the input buffer exceeds 256 bytes,
the printer transfers a DC1 (11H: Data Receive Ready) signal to the host.
(4) GND
Common GND on the circuit.

7.3 Error Detection

Parity, framing, and overrun are detected. On detection of any error, the data are stored in the
buffer as "?".
(1) Framing Error
With "space" state having been detected on detection of a stop bit, error takes place.
The data are stored in the buffer as "?".
(2) Parity Error
With an error having been detected under specifying parity check, the data is stored in the buffer
as "?".
(3) Overrun Error
On detection of an overrun error, the data are stored in the buffer as "?".

7.4 Data Receiving Control

When DTR/DSR control having been selected, with BUSY signal at "LOW", data from the host
side are received. With the signal at "HIGH", they can not be received.
When DTR/DSR control not having been selected, after X-ON transmission, data is received
from the host side. No transmission of data can take place after X-OFF is transmitted.
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BD2-2880/2890 User's Manual