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What is the RS232 communication pinout for the Micom Relays?

Title
RS232 pinouts for communication with Micom Relays using a computer

Issue
Various USB to RS232 cables are available in the market and the pinouts help pick the right one for good communication

Product Line
Micom Relays

Environment
RS232 front port communications

Cause
Cable with crossover communication pins result in unsuccessful communication

Resolution
The relay is a Data Communication Equipment(DCE) device. Hence the pin connections of the relay's 9-pin front port are as follows:

Pin no.2                     Tx Receive Data

Pin no.3                     Rx Transmit Data

Pin no.5                     0V Zero volts Common

None of the other pins are connected in the relay. 

PC's are normally Data Terminal Equipment (DTE) devices which have a serial port connection as below:

Pin no.2                     Rx Receive Data

Pin no.3                     Tx Transmit Data

Pin no.5                     0V Zero volts Common

For successful data communication, the Tx pin on the relay must be connected to the Rx pin on the PC, and the Rx pin on the relay must be connected to the Tx pin on the PC.

Therefore, providing that the PC is a DTE, a "straight through" serial connector is required i.e one that connects pin 2 to pin 2, pin 3 to pin 3 and pin 5 to pin 5 as shown below



Note: A common cause of difficulty with serial data communication is connecting Tx to Tx and Rx to Rx. This could happen if a 'cross-over' serial connector is used, i.e. one that connects pin2 to pin3, and pin 3 to pin 2, or if the PC has the same pin configuration as the relay




 
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