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CMOS to RS232 converter | RS232 to CMOS converter

This page describes CMOS to RS232 converter and RS232 to CMOS converter.

CMOS to RS232 converter

CMOS to RS232 converter

Figure-1 depicts simple CMOS to RS232 converter. It converts CMOS signal levels to RS232 signal levels. Following table-1 mentions CMOS side pin descriptions and signal designations. The converter uses MAX232 IC for RS232 to TTL level conversion.


CMOS Pin Descriptions
TXD- 3 (Output)
RXD- 2 (Input)
RTS- 7 (Output)
CTS- 8 (Input)
GND 5 (Signal Ground)

Table-1:CMOS Side Pins (DB9 Male)

Following table-2 mentions RS232 side pin descriptions and signal designations.


RS232 Pin Descriptions
RXD 3 (Input)
TXD 2 (Output)
CTS 7 (Input)
RTS 8 (output)
GND 5 (Signal Ground)

Table-2:RS232 Side Pins (DB9 Female)

In order to constuct CMOS to RS232 converter, Connections should be made as mentioned above one to one. Moreover voltage conversions should be taken care between RS232 voltage levels and CMOS voltage levels for logic 1 ("HIGH") and logic 0 ("LOW") as described below in table-3.

RS232 to CMOS converter

The RS232 to CMOS converter does reverse of the above functionality. It converts RS232 signal levels to CMOS signal levels. The same cable as mentioned above can be used with proper mating connectors.

Logic Type RS232 CMOS
Logic 1 >+5V (at output), >+2.4V(at input) >2.4V (at output), >2V (at input)
Logic 0 <-5V (at output) <0.2V (at input) <0.55V(at output), <0.8V (at input)

CMOS to RS232 converter has following applications:
• Provide RS232 to CMOS and viceversa adaptation
• Mostly will have four signal conversion.
• Supports baud rate upto 115.2 Kbps
• External power is not needed, embedded IC derive its power from port connected with the system such as laptop, PC etc.

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