RS232 to TTL converter | TTL to RS232 converter

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

RS232 to TTL converter

RS232 to TTL converter

Figure-1 depicts simple RS232 to TTL converter. It converts RS232 signal levels to TTL signal levels. Following table-1 mentions RS232 side pin descriptions and signal designations.

RS232 Pin Descriptions
2 (RXD) Receive Data input
3 (TXD) Transmit Data output
7 (RTS) Request to Send
8 (CTS) Clear to Send

Table-1:RS232 Side Pins

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

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

Table-2:TTL Side Pins

TTL to RS232 converter

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

In TTL logic family, logic-1 and logic-0 are represented as follows while RS232 logic levels are represented as follows.

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

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