Contact Info

Crumbtrail » Serial Port Component » Tutorials » RS449

RS449 Serial Port Connector Pin Layout

RS-449 is a serial communications standard that provides asynchronous communication capabilities, such as hardware flow control, software flow control, and parity check. It has been widely used for decades.

RS449 is a high speed digital interface - unlike RS232 which uses signals with reference to ground, RS449 V.11 receivers look for the difference between two wires. By twisting the two wires and making a "twisted pair" any stray noise picked up on one wire will be picked up on the other, because both wires pick up the same noise the RS449 differential interface just shifts in voltage level with reference to ground, but does not change with respect to each other. The receivers are only looking at the difference in voltage level of each wire to the other not to ground.

The following document describes the functions of the pins on the RS449 9 and 37 pin Sub-D connectors used in serial communications. The pins in the images are as viewed from the pin side (not the solder or printed circuit board side). The male sockets are used on the DTE (Data Terminal Equipment ) or PC side. The female sockets are on the DCE (Data Communication Equipment ) or Modem Side.

Using the ActiveXperts Serial Port Component you can send and receive data and control the RS422 port.

RS449 9 Pin connector (DB-9)

RS449 9 Pin connector (DB-9)
1 GND Shield
2 SSR Secondary Receiver Ready
3 SSD Secondary Send Data
4 SRD Secondary Receive Data
5 SG Signal Ground
6 RC Receive Common
7 SRS Secondary Request To Send
8 SCS Secondary Clear To Send
9 SC Send Common

RS449 37 Pin connector (DB-37)

RS449 37 Pin connector (DB-37)
1 GND Ground
2 SRI Signal Rate Indicator
3 - Reserved
4 TDA Transmit Data A
5 TTA Transmit Timing A
6 RDA Received Data A
7 RTSA Request To Send A
8 RTA Receive Timing A
9 CTSA Clear To Send A
10 LL Local Loopback
11 DMA Data Mode A
12 DTRA Data Terminal Ready A
13 RRA Receiver Ready A
14 RL Remote Loopback
15 IC Incoming Call
16 SF/SR Select Frequency/Select Rate
17 TTA Terminal Timing A
18 TMA Test Mode A
19 GND Ground
20 RC Receive Common
21 - Not Connected
22 TDB Transmit Data B
23 TTB Transmit Timing B
24 RDB Receive Data B
25 RTSB Request To Send B
26 RTB Receive Timing B
27 CTSB Clear To Send B
28 TIS Terminal In Service
29 DMB Data Mode B
30 DTRB Data Terminal Ready B
31 RRB Receiver Ready B
32 SS Select Standby
33 SQ Signal Quality
34 NS New Signal
35 TTB Terminal Timing B
36 SB Standby Indicator
37 SC Send Common