CyberResearch CYB 2232C, User Manual, Page: 15 / 20

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CHAPTER 4 RS-232 PINOUTS AND PORT CABLING.
Introduction
This chapter gives details of the 9- and 25-pin RS-232 pin outs, cabling and connections, with
information on how to connect the serial ports of two PCs and how to make a self-test loop-back
connector.
The RS-232 Standard
RS-232 is a slow, short distance, single ended transmission system (i.e., only one wire per signal).
Typical RS-232 maximum cable length is 50 feet with a maximum data rate of 20K bits per second.
Figure 4-1. RS-232 Point-to-Point Connection.
RS-232C Standard
1 Driver 1 Receiver
Line Length Max Data Rate
50 Feet = 15m 20 Kbits/sec
Serial Port Pin Outs
The pin outs of the 9- and 25-pin Male D connectors are given below.
Figure 4-2. Serial Port RS-232
9-Pin Connector:
25-Pin Connector:
D TTL
Ground Ground
TTL R
PIN 7 - GROUND (GND)
PIN 2 - TRANSMITTED DATA (TXD)
PIN 3 - RECEIVED DATA (RXD)
PIN 4 - REQUEST TO SEND (RTS)
PIN 6 - DATA SET READY (DSR)
PIN 5 - CLEAR TO SEND (CTS)
PIN 8 - DATA CARRIER DETECT (DCD)
PIN 20 - RING INDICATOR (RI)
PIN 22 - DATA TERMINAL READY (DTR)
PIN 1 - DATA CARRIER DETECT (DCD)
PIN 6 - DATA SET READY (DSR)
PIN 8 - CLEAR TO SEND (CTS)
PIN 3 - TRANSMITTED DATA (TXD)
PIN 2 - RECEIVED DATA (RXD)
PIN 4 - DATA TERMINAL READY (DTR)
PIN 7 - REQUEST TO SEND (RTS)
PIN 9 - RING INDICATOR (RI)
PIN 5 - GROUND (GND)