HP C3916A HP LaserJet 5, 5M, and 5N Printer - User's Guide - Page 192

Pin Functions

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Pin Functions Pin 1Protective Ground This pin is also referred to as chassis ground and should not be confused with pin 7, or common ground which serves as the circuit common. The purposed of this pin is to provide protection against electrical shock where two pieces of equipment are connected and one piece does not include a ground connection, or round prong on its AC plug. In some cases not connecting chassis ground may disable communication or connecting these pins may create a problem known as a ground loop. Both of these situations are rare in general and in most cases pin 1 is not needed to establish communication between two devices. Questions regarding the need for connecting or not connecting chassis ground should be referred to an electrical expert. Pin 2Transmitted Data (TxD or TD) This pin transmits data. Pin 3Received Data (RxD or RD) This pin receives data. Pin 4Request to Send (RTS) General purpose output. Uses vary widely. In half-duplex modems this is used to signal a desire to transmit data. Pin 5- General purpose input. Uses vary widely. In half-duplex modems this is used to grant permission Clear to Send (CTS) to transmit. Pin 6Data Set Ready (DSR) General purpose input to signal that the DTE and the DCE is powered up and ready to go. Pin 7Common Reference point for all interface voltages. Pin 8Data Carrier Detect (DCD) On modems DCD is asserted when connected to a remote modem. On a DTE it is frequently used to disable data reception. Pin 20Data Terminal Ready (DTR) General purpose output. Generally used to signal to the DCE that the DTE has been powered up and is ready to go. E-4 Serial Pin-out and Cabling Configuration EN

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Pin Functions
Pin 1-
Protective Ground
This pin is also referred to as chassis ground and should not be confused with pin 7, or common
ground which serves as the circuit common.
The purposed of this pin is to provide protection
against electrical shock where two pieces of equipment are connected and one piece does not
include a ground connection, or round prong on its AC plug. In some cases not connecting
chassis ground may disable communication or connecting these pins may create a problem
known as a ground loop.
Both of these situations are rare in general and in most cases pin 1 is
not needed to establish communication between two devices. Questions regarding the need for
connecting or not connecting chassis ground should be referred to an electrical expert.
Pin 2-
Transmitted Data
(TxD or TD)
This pin transmits data.
Pin 3-
Received Data
(RxD or RD)
This pin receives data.
Pin 4-
Request to Send
(RTS)
General purpose output.
Uses vary widely.
In half-duplex modems this is used to signal a desire
to transmit data.
Pin 5-
Clear to Send (CTS)
General purpose input.
Uses vary widely.
In half-duplex modems this is used to grant permission
to transmit.
Pin 6-
Data Set Ready
(DSR)
General purpose input to signal that the DTE and the DCE is powered up and ready to go.
Pin 7-
Common
Reference point for all interface voltages.
Pin 8-
Data Carrier Detect
(DCD)
On modems DCD is asserted when connected to a remote modem.
On a DTE it is frequently
used to disable data reception.
Pin 20-
Data Terminal
Ready (DTR)
General purpose output.
Generally used to signal to the DCE that the DTE has been powered up
and is ready to go.
E-4
Serial Pin-out and Cabling Configuration
EN