MODEL232BSS4 B&B Electronics, MODEL232BSS4 Datasheet - Page 22

• Manufacturer Part Number: MODEL232BSS4
• Description: Buffered Smart Switch
• Manufacturer: B&B Electronics

Chapter 3: PORT CONNECTIONS
DTE/DCE Explanation
232BSS4, it is necessary to have a basic understanding of the terms
DTE and DCE. RS-232 was designed, using DB-25 connectors, for
connecting a DTE (Data Terminal Equipment) device to a DCE (Data
Communication Equipment) device. Each device will have inputs on
pins that correspond to outputs on the same pins of the other device.
For example, a DTE device will transmit data out on pin 2 (on a DB-
25) and a DCE device will receive data in on pin 2 (on a DB-25). IBM
PCs and serial printers are DTE devices, modems are DCE devices.
connector. Since then, the use of a 9 pin D-Sub supporting only a
portion of the original RS-232 signals has been used extensively,
starting with the IBM PC and migrating into other peripherals. The
pinouts for this 9 pin connector have since become the EIA/TIA 574
standard. This standard specifies a DTE device that transmits on pin
3 and receives on pin 2, with the DCE having the opposite
configuration.
20
25 Pin DTE
DEVICE
Originally the RS-232 standard specified only a 25 pin D-sub
In order to determine the proper port connections to the
T
T
T
R
R
R
R
2 (TD)
3 (RD)
4 (RTS)
5 (CTS)
20 (DTR)
6 (DSR)
8 (DCD)
7 (GND)
LINE
T = RS-232 Transmitter
Figure 3.1. DTE/DCE Port Diagrams
25 Pin DCE
LINE
2 (TD)
3 (RD)
4 (RTS)
5 (CTS)
20 (DTR)
6 (DSR)
8 (DCD)
7 (GND)
DEVICE
R
R
R
T
T
T
T
Documentation Number 232BSS41202 Manual
9 Pin DTE
DEVICE
R = RS-232 Receiver
T
T
T
R
R
R
R
3 (TD)
2 (RD)
7 (RTS)
8 (CTS)
4 (DTR)
6 (DSR)
1 (DCD)
5 (GND)
LINE
LINE
9 Pin DCE
3 (TD)
2 (RD)
7 (RTS)
8 (CTS)
4 (DTR)
6 (DSR)
1 (DCD)
5 (GND)
DEVICE
R
R
R
T
T
T
T