Communication interfaces, Serial interface – Bematech KC-4112 Rev.1.0 User Manual

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Figure 14

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Communication between a host and the printer can be performed in two communication protocols: Parallel or Serial
RS-232, according to the printer model.

Communication cables are not supplied with the printer

Serial Interface

The RS232 serial interface uses a female DB-25 connector. The serial port can operate using the DTR/DSR
mode, with 7 or 8 data bits, with or without parity, even or odd parity, one start bit and one or more stop bits. In
the RS232 standard, the logic low level corresponds to a +12V voltage level and a logic high level corresponds
to a –12V voltage level.

DTR / DSR mode

In this mode, the printer’s DTR line controls the flow of data sent from the host’s TX line and received by the
printer’s RX pin. In this case, when the printer’s DTR signal is low (+12V) the printer requests the host to send
data. When the DTR signal is high (-12V) the printer tells the host to stop sending data.

DB-25 Serial connector

Chapter 4

Communication Interfaces

The serial cable needed for the DTR / DSR mode is shown below:

Printer Side (DB-25)

Host Side (DB-9)

2 (TD)

2 (RD)

3 (RD)

3 (TD)

6 (DSR)

4 (DTR)

7 (GND)

5 (GND)

20 (DTR)

6 (DSR)

1-7-8 (jumper)