C.2. RS-232C/RS-422A Interface

C.2. RS-232C/RS-422A Interface

RS-232C interface

Interface Signals

The pins of the printer's RS-232C interface connector carry the signals listed in Table C.2. The table also indicates whether each signal is incoming or outgoing with respect to the printer.

Table C.2. RS-232C Signal Pin Assignments

Pin

In/out

Signal

Description

 

 

 

 

1

–

FG

Frame ground

 

 

 

 

2

Out

TXD

Transmit Data

 

 

 

 

3

In

RXD

Receive Data

 

 

 

 

4

Out

RTS

Request To Send

 

 

 

 

5

In

CTS

Clear To Send

 

 

 

 

6

In

DSR

Data Set Ready

 

 

 

 

7

–

SG

Signal Ground

 

 

 

 

20

Out

DTR

Data Terminal Ready

 

 

 

 

Brief descriptions of the signals follow.

FG - Frame Ground - (Pin 1)

This pin is connected directly to the printer frame.

TXD - Transmit Data - (Pin 2)

This output carries asynchronous data sent by the printer to the computer. It is used mainly in handshaking protocols.

RXD - Receive Data - (Pin 3)

This input carries serial asynchronous data sent by the computer to the printer.

RTS - Request To Send - (Pin 4)

This output is always held high (above 3 volts).

CTS - Clear To Send - (Pin 5)

DSR - Data Set Ready - (Pin 6)

Unused.

SG - Signal Ground - (Pin 7)

All signals can transmit between the printer and the host computer to send each signals with a signal ground.

DTR - Data Terminal Ready - (Pin 20)

This output is used as a buffer nearly-full handshake line. It is held high (above 3 volts) when the buffer can accept more data.

RS-232C Interface Voltage Levels

The voltage levels of the interface signals conform to EIA RS-232C specifications. SPACE is from 3 volts to 15 volts. MARK is from -3 volts to -15 volts. Voltages between -3 volts and 3 volts are undefined.

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