Sun Microsystems Interface Adapter manual RS-449 Interface Signals

Interface Signals

Functional descriptions of the RS-449 interface signals are provided in TABLE A-2.

TABLE A-2	RS-449 Interface Signals
RS-449 Pin
Number	Signal Name	Function
1	Shield Ground	Enables tandem sections of shielded cable to retain
		continuity through the connector.
19	Signal Ground	Directly connects the DTE circuit ground to the DCE
	(SG)	circuit ground, providing a path for DTE and DCE
		signal commons.
4/22	Transmit Data	Used by the DTE to pass binary data to the DCE for
	(TxD)	transmission over the communications channel.
6/24	Receive Data	Used by the DCE to pass binary data received from the
	(RxD)	communications channel to the DTE.
5/23	Transmit Clock in	Enables the DCE to transmit signal element timing to
	(TxCI)	the DTE. This enables the DTE Transmit Data signal on
		circuit TxD to be in synchronization with On/Off
		transitions on this lead.
8/26	Receive Clock	Transitions on this lead enables the DTE to time data
	(RxC)	received over circuit RxD.
17/35	Transmit Clock	Enables the DTE to provide transmit timing
	(TxC)	information to the DCE so that the DTE can
		synchronize with data arriving over the TxD lead.
7/25	Request to Send	Used by the DTE to advise the DCE it is ready to
	(RTS)	transmit data.
9/27	Clear to Send	Used by the DCE to advise the DTE that the DCE is
	(CTS)	ready to send data over the communications channel.
11/29	Data Set Ready	Used to advise the DTE of the Ready status on the
	(DSR)	DCE. In most cases, this signal simply implies the unit
		is powered on.
12/30	Data Terminal	Used by the DTE to advise the DCE it is ready to
	Ready (DTR)	transmit or receive.
13/31	Data Carrier Detect	The DCE uses this lead to advise the DTE that an
	(DCD)	incoming signal on the communications channel is
		present. When first initialized this signal is an
		indication to the DTE to expect data momentarily.

Appendix A Cable Pin Assignments & Signals 27