Understanding Power Requirements In RS-232 Applications Datasheet

Understanding Power Requirements in RS-232 Applications

As the popularity of asynchronous serial communication became widely accepted by the industry, the RS-232 standard gained very wide acceptance. The use of this standard is visible in almost all Industrial, Portable, Desktop, Data Acquisition and Test Measurement applications using a serial port for communication. Even though the standard specifies a maximum data rate for RS-232 of 20 kbps, some applications need for higher speed is overwhelming. More and more applications today require at least 120 kbps to support Laplink®, a popular communication software used by Laptop/Desktop computers for fast file transfer between two computers. RS-232 type Drivers and Receivers must also support this higher data rate to be Laplink compatible.

This application note covers the RS-232 circuit functions, an explanation of hardware handshaking, a step by step analysis of the hardware handshaking between a local and remote terminal, and power requirements/dissipation of the DS14C335.
RS-232 HANDSHAKING CIRCUITS.

In a Terminal (DTE-Data Terminal Equipment) to Modem (DCE-Data Circuit Terminating Equipment) application, as shown in Figure 2, commonly only eight dedicated lines are required. Even though the standard defines a 25 pin connection, the de-facto 9 pin connector is very popular. These lines are DCD, RXD, TXD, DTR, DSR, RTS, CTS, RI and GND and are shown in Figure 1. Lets take a quick look at these dedicated lines along with their respective functions. Note that ON is defined as a positive voltage and OFF is a negative voltages on the cable.

Notice: we do not provide any warranties that information, datasheets, application notes, circuit diagrams, or software stored on this website are up-to-date or error free. The archived Understanding Power Requirements In RS-232 Applications Datasheet file may be downloaded here without warranties.