1. NARNARAYAN SHASTRI INSTITUTE OF TECHNOLOGY Prepared by: Wasu Ichcha kaur H. 130340111031 Bhalani Nidhi M. 130340111003 Dhakate Megha D. 130340111005 MICROCONTROLLER

2. RS 232 STANDARD

3. OVERVIEW Introduction RS 232 Serial communication Signals used in RS-232 Pins on RS-232 interface DB-25 connector Features Signal specification Data transmission & reception

4. INTRODUCTION The RS-232C standard is an asynchronous serial communication method. RS-232 is a standard by which two serial devices communicate: – The connection must be no longer than 50 feet. – Transmission voltages are –15V and +15V. – It is designed around transmission of characters (of 7 bits of length). It formally defines the signals connecting between a DTE (data terminal equipment) such as a computer terminal, and a DCE (data circuit-terminating equipment) such as a modem.

5. The RS-232 standard is commonly used in computer serial ports. The RS-232C standard works at the physical layer of the communication standard. This is the lowest level and the one that physically connects the devices. The communication is done through the serial port of the PC. This is a male connector with 25 (old) or 9 (new) pins, in both cases only 9 pins, at the most, are used

6. RS-232 SERIAL COMMUNICATION The EIA RS-232 serial communication standard is a universal standard, originally used to connect teletype terminals to modem devices. Figure of serial communication in next slide shows a PC connected to a device such as modem or a serial printer using the RS-232 connection. In modern PC the RS-232 interface is referred to as a COM port. The COM port uses a 9-pin D-type connector to attach to RS- 232 cable. The RS-232 standard defines a 25-pin D-type connector but in newer systems connector is reduced to a 9-pin device so as to reduce size

7. SERIAL COMMUNICATION

8. 9 Pin Connector on a DTE device (PC connection) Male RS232 DB9 Pin NumberDirection of signal: 1Carrier Detect (CD) (from DCE) Incoming signal from a modem 2Received Data (RD) Incoming Data from a DCE 3Transmitted Data (TD) Outgoing Data to a DCE 4Data Terminal Ready (DTR) Outgoing handshaking signal 5Signal Ground Common reference voltage 6Data Set Ready (DSR) Incoming handshaking signal 7Request To Send (RTS) Outgoing flow control signal 8Clear To Send (CTS) Incoming flow control signal 9Ring Indicator (RI) (from DCE) Incoming signal from a modem SIGNALS USED IN RS232

9. RS-232 DB-9 Connector

10. PINS ON RS-232 C INTERFACE DB-25 CONNECTOR

11. SpecificationsRS232 Mode of operationSingle ended number of drivers/receivers on one line1 driver, 1 receiver maximum cable length50 feet maximum data rate460kbps max. driver output voltage+/- 25 V Max. driver current in high impedance state+/-6mA at +/-2V slew rate(max)30 V/µS receiver input voltage range+/-15V Receiver input sensitivity+/-3V Driver load impedance3K to 7K Ohms Receiver Input Resistance3K to 7K Ohms HARDWARE SPECIFICATION OR FEATURES

12. SIGNAL SPECIFICATION DCD- Data Carrier Detect, signal from DCE to DTE. Indicates that modem (DCE) is busy i.e. already using the line. RTS- Request to Send, DTE requests DCE to become ready to accept the data. CTS- Clear to Send, DCE acknowledges DTE that I am ready to receive the data. (Response of RTS). DTR- Data Terminal Ready, DTE is ready to transmit. DSR- Data Set Ready, DCE is ready to receive. SGND- Signal Ground

13. DATA TRANSMISSION AND RECEPTION USING RS-232 Modem and other devices used to send serial data, are called as DCE i.e. Data Communication Equipments. The computers that transfer or receive serial data are called as DTE i.e. Data Terminal Equipments. The signal and handshake signals are transferred between DTE and DCE.

14. DTE & DCE CONNECTION DIAGRAM