Bai giang RS232_phan 2 pptx

Serial Communication EIA RS232, RS422 and RS485 Recommended Standard 232 The purpose of this course note is to attempt to describe the main elements in Serial Communication. This application note attempts to cover enough technical details of RS232, RS422 and RS485. EIA - Electroonic Industries Association D-subminiature • The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. • A, B, C, D, or E denoting the shell size, followed by the number of pins or sockets, followed by either P (plug) – M(Male) or S (socket) – F (Female) RS232 is an asynchronous or synchronous serial communications protocol • Personal computers first used DB25 connectors for their serial and parallel ports EIA232 communication function and connector types for a personal computer and modem. DCE devices are sometimes called "Data Communications Equipment" instead of Data Circuit-terminating Equipment. RS-232C RS-232 stands for Recommend Standard number 232 and C is the latest revision of the standard. The serial ports on most computers use a subset of the RS-232C standard. The full RS-232C standard specifies a 25-pin "D" connector of which 22 pins are used. Most of these pins are not needed for normal PC communications, and indeed, most new PCs are equipped with male D type connectors having only 9 pins. RS232 on DB25 (RS-232C) The public switched telephone network (PSTN) is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by switching centers, thus allowing any telephone in the world to communicate with any other. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core and includes mobile as well as fixed telephones. When the PC serial port began to use 9-pin connectors, they were often labeled as DB9 instead of DE9 connectors, due to an ignorance of the fact that B represented a shell size. It is now common to see DE9 connectors sold as DB9 connectors. RS232 on DB9 (EIA/TIA 574) RS232 DB25 to DB9 converter RS232 DB9 pinout RS232 DB25 pinout RS232 DB9 to DB25 converter DB9 - DB25 conversion DB9 DB 25 Function 1 8 Data carrier detect 2 3 Receive data 3 2 Transmit data 4 20 Data terminal ready 5 7 Signal ground 6 6 Data set ready 7 4 Request to send 8 5 Clear to send 9 22 Ring indicator Connects any serial modem with DB25 to PC DB9 serial EIA 561 RS232D uses RJ45 type connectors (similar to telephone connectors) RS232 on RJ45 (RS-232D) MODEM COMMUNICATION BETWEEN TWO PC’S RS232 DB9 pinout RS 232 Voltage levels SIGNAL VOLTAGE LEVELS VOLTS LOGICAL STATE -3 to -25 1 +3 to +25 0 CONTROL VOLTAGE LEVELS VOLTS LOGICAL STATE -3 to -25 OFF +3 to +25 ON - The signal ground, ie. the reference level for all signals. - The protective ground : Also known as Shield Ground. This is the chassis ground connection between DTE and DCE. It should not be used as a signal ground, and it must not be connected to signal ground. Connecting protective ground on both sides makes sure that no large currents flow through Signal ground in case of an insulation defect on one side [...]... The first step to connecting a device to the RS -23 2 port is to transform the RS -23 2 levels into 0 and 5 Volts, AND, this is done by RS -23 2 Level Converters The MAX -23 2 It includes a Charge Pump, which generates +10V and -10V from a single 5v supply This I.C also includes two receivers and two transmitters in the same package RS -23 2 Level Converters RS -23 2 Level Converters Relationship of Baud Rate to... DCE devices Null Modem RS2 32 Lead Asynchronous (RS -23 2) serial link universal asynchronous receiver/transmitter or UART Electrical characteristics Charge Pump Voltage Doubler Charge Pump Voltage Inverter By Reversing the position of the Vout and Vin, the regulator becomes fractional gain (1 /2) Example 0 The signal level inversion (logic 1 is -12V and logic 0 is +12V) RS -23 2 Level Converters The first... unstable conditions that happen when you send a "pulse" down the wire and change voltages too quickly Baud Rate 24 00 4800 9600 1 920 0 Maximum Distance (in feet) 3000 1000 500 50 Maximum Distance (in meters) 914.4 304.8 1 52. 4 15 .24 TYPICAL RS 23 2 MODEM APPLICATION Processor UART Peripheral RS -23 2 Transceiver COM1 DB-9 connector . connectors. RS2 32 on DB9 (EIA/TIA 574) RS2 32 DB25 to DB9 converter RS2 32 DB9 pinout RS2 32 DB25 pinout RS2 32 DB9 to DB25 converter DB9 - DB25 conversion DB9 DB 25 Function 1. serial modem with DB25 to PC DB9 serial EIA 561 RS232D uses RJ45 type connectors (similar to telephone connectors) RS2 32 on RJ45 (RS -23 2D) MODEM COMMUNICATION