DocID9986 Rev 2

11/22

AN1753

Hardware setup

5

Hardware setup

A general system configuration is shown in Figure 1. The ST7FLITE0 is connected to an

RS-232 line driver chip which is in turn connected to any RS-232-compatible device. The

RS-232 line driver is needed to convert the 5-volt logic level of the ST7FLITE0 to the proper

RS-232 line voltages, and vice versa.

Figure 4 shows a specific example of a hardware setup required for UART in which the

ST7FLITE0 processor and RS-232 Driver/ Receiver are used. You can use different

driver/receiver in your application. For example, you can use an MC14C88/ 89 as a low cost

solution.

The Receive Data pin (RD) of the PC serial port must correspond to the PA3 pin of the

ST7FLITE0, and the Transmit Data pin (TD) to the PA7 pin.

Caution:

The three main devices (PC, ST7LITE0, MAX232) must have the same electrical reference

(GND). For a detailed description of MAX232, please refer to the datasheet.

Figure 4. Test Setup

PC

TERMINAL

serial port

TD

RD

GROUND

MAX232

IN

OUT

OUT

IN

ST7FLITE0

GND

GND

GND

PA7 pin

PA3 pin