DB-25 Serial/Com Port refers to a 25 – pin serial communication port, which is an interface that complies with the RS – 232C standard and is mainly used for asynchronous data transmission1. The following is a detailed introduction:
Replacement and Compatibility1: With the development of equipment, the DB – 25 interface is gradually replaced by the DB – 9 interface. The DB – 9 interface only provides 9 signals for asynchronous communication, and its commonly used pins are different from those of the DB – 25. When connecting with a DCE device equipped with a DB – 25 connector, a special cable must be used.
Pin Definition1: The DB – 25 connector defines 25 signal lines, which are divided into 4 groups. They are 9 voltage signals for asynchronous communication (including signal ground SG), 9 20mA current – loop signals, 6 empty pins, and 1 protective ground (PE) as the device grounding terminal.
Electrical Characteristics1: In RS – 232C, which is the standard followed by DB – 25 serial ports, the logic level of data is defined as logic 1 (MARK) = – 3V～- 15V, and logic 0 (SPACE) = + 3～＋15V. For control signals, the effective signal (ON state) = + 3V～+ 15V, and the invalid signal (OFF state)=-3V～-15V.
Application Scenarios2: The male DB – 25 is mainly used as the COM2 port of the computer, and various RS – 232 communication devices use the male version. The female DB – 25 is mainly used as the computer printer port.
Cable Connection3: When the communication distance is short (<12m), the standard RS232 port can be directly connected by a cable. The simplest and most commonly used connection method is the three – wire connection, that is, the ground, receive data, and send data pins are connected.
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