Serial Communication
All communication we have dealt with up to now has been parallel. Data being transferred between one location and another (R0 to the accumulator, for example) travel along the 8-bit data bus. Because of this data bus, data bytes can be moved about the microcontroller at high speed.
However, parallel communication has the disadvantage of requiring at least eight separate lines (in an 8-bit system) and in most cases extra lines to synchronize the data transfer (in the case of the microcontroller, the control bus).
Serial communication has the advantage of requiring only one line for the data, a second line for ground and possibly a third line for the clock. Therefore, because serial communication requires less physical wires, it is more suitable for transmitting data over longer distances.
The obvious disadvantage of serial communication, compared with parallel, is the reduction in the data transfer rate. If we imagine a system where it takes 1us for data to settle on the data bus, we could say it takes 1us to transfer a data byte using parallel communication. If we imagine the same timeframe for data bits settling on the serial line, it would take 8us to transfer a data byte using serial communication (1us for each bit).
Synchronous Serial Communication
Synchronous serial communication requires an extra line for the clock signal. For serial communication, the 8-bit parallel data byte must be shifted down the serial line (in transmission). Therefore, one bit is followed by another. Some kind of system must be used to determine how long each bit is on the line. For example, the serial system designer may decide each bit will be on the line for 1us and, as explained above, transmission of the full eight bits would take 8us.
Asynchronous Serial Communication
A good example of asynchronous serial communication is the interface between a keyboard and a computer. In this case, the keyboard is the transmitter and the computer is the receiver. With asynchronous communication, a clock signal is not sent with the data. There are a number of reasons why this form of communication might be desirable over synchronous communication. One advantage is the fact that the physical line for the clock is not needed. Also, asynchronous communication is better over long distances. If we try to synchronize a remote receiver by sending the clock signal, due to propagation delays and interference, the validity of the clock is lost.
Another reason for not transmitting the clock arises when the data rate is erratic. For example, data rate from a keyboard to a computer is dependent upon the typist. The user may type at a rate of sixty words per minute, but at other times he/she may type a lot less. And for long periods there may be no data sent at all. Because of this erratic data rate an asynchronous communication system is suitable.
The 8051 Serial Port
The 8051 includes an on-chip serial port that can be programmed to operate in one of four different modes and at a range of frequencies. In serial communication the data is rate is known as the baud rate, which simply means the number of bits transmitted per second. In the serial port modes that allow variable baud rates, this baud rate is set by timer 1.
The RS232 connector was originally developed to use 25 pins. In this DB25 connector pinout provisions were made for a secondary serial RS232 communication channel. In practice, only one serial communication channel with accompanying handshaking is present. Only very few computers have been manufactured where both serial RS232 channels are implemented. Examples of this are the Sun SparcStation 10 and 20 models and the Dec Alpha Multia. Also on a number of Telebit modem models the secondary channel is present. It can be used to query the modem status while the modem is on-line and busy communicating. On personal computers, the smaller DB9 version is more commonly used today. The diagrams show the signals common to both connector types in black. The defined pins only present on the larger connector are shown in red. Note, that the protective ground is assigned to a pin at the large connector where the connector outside is used for that purpose with the DB9 connector version.
The DB9 (originally DE-9) connector is an analog 9-pin plug of the D-Subminiature connector family (D-Sub or Sub-D).
The DB9 connector is mainly used for serial connections, allowing for the asynchronous transmission of data as provided for by standard RS-232 (RS-232C).
The only thing left is that we need some sort of connector to connect to the serial port. The sample code below is written for Comm1 and most computers use a 9 pin DB9 male connector for Comm1 so a 9 pin female connector is included for this project. We also need a DB9 extension cable to make the connection easier. There should be 3 wires soldered to the DB9 connector pins 2, 3 and 5. Connect the wire from pin 5 of the connector to ground on the breadboard. Connect the wire from pin 2 of the connector to pin 14 of the MAX232.
DB9 pin connector for RS232 serial Communication between humidity monitoring project and computer.
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DB9 pin connector for RS232 serial Communication,db9 pinout,db9 connector,db9 cable,db9 price,db9 serial port,aston martin,rs232,db9 serial
rs232 db9 connector,db9 connector datasheet,db25 connector,outlook connector,keyboard with 9 pin d connector,mini din connector,db9 connector configuration,15 pin,Converts a USB port into a 9-pin male RS-232 serial port, DB9 Serial Cables, DB9 mice mouse cable Cables Serial Cable Computer Cables Computer Cable Switch Box USB Switch boxes Monitor Cables Assembly cables.Shop for DB9 Cable Cables and Connectors Computer Accessories and read product reviews. Find cheap prices on DB9 Cable Cables and Connectors Computer,Serial (RS232) null modem cable (DB9-DB9). Pinout and signals for building a serial (RS232) nullmodem cable. Use this cable between two DTE devices,RS232 serial cables and adapters. Pinout and wiring layout for many situations. DB9 to DB25 conversion and null modem wiring diagrams.This creates an electrically continuous screen covering the whole cable and connector ... It is now common to see DE9 connectors sold as "DB9" connectors.Cables To Go offers a wide selection of DB9 RS-232 Cables ready to ship today! Need help? Chat with one of our cable experts.
All communication we have dealt with up to now has been parallel. Data being transferred between one location and another (R0 to the accumulator, for example) travel along the 8-bit data bus. Because of this data bus, data bytes can be moved about the microcontroller at high speed.
However, parallel communication has the disadvantage of requiring at least eight separate lines (in an 8-bit system) and in most cases extra lines to synchronize the data transfer (in the case of the microcontroller, the control bus).
Serial communication has the advantage of requiring only one line for the data, a second line for ground and possibly a third line for the clock. Therefore, because serial communication requires less physical wires, it is more suitable for transmitting data over longer distances.
The obvious disadvantage of serial communication, compared with parallel, is the reduction in the data transfer rate. If we imagine a system where it takes 1us for data to settle on the data bus, we could say it takes 1us to transfer a data byte using parallel communication. If we imagine the same timeframe for data bits settling on the serial line, it would take 8us to transfer a data byte using serial communication (1us for each bit).
Synchronous Serial Communication
Synchronous serial communication requires an extra line for the clock signal. For serial communication, the 8-bit parallel data byte must be shifted down the serial line (in transmission). Therefore, one bit is followed by another. Some kind of system must be used to determine how long each bit is on the line. For example, the serial system designer may decide each bit will be on the line for 1us and, as explained above, transmission of the full eight bits would take 8us.
Asynchronous Serial Communication
A good example of asynchronous serial communication is the interface between a keyboard and a computer. In this case, the keyboard is the transmitter and the computer is the receiver. With asynchronous communication, a clock signal is not sent with the data. There are a number of reasons why this form of communication might be desirable over synchronous communication. One advantage is the fact that the physical line for the clock is not needed. Also, asynchronous communication is better over long distances. If we try to synchronize a remote receiver by sending the clock signal, due to propagation delays and interference, the validity of the clock is lost.
Another reason for not transmitting the clock arises when the data rate is erratic. For example, data rate from a keyboard to a computer is dependent upon the typist. The user may type at a rate of sixty words per minute, but at other times he/she may type a lot less. And for long periods there may be no data sent at all. Because of this erratic data rate an asynchronous communication system is suitable.
The 8051 Serial Port
The 8051 includes an on-chip serial port that can be programmed to operate in one of four different modes and at a range of frequencies. In serial communication the data is rate is known as the baud rate, which simply means the number of bits transmitted per second. In the serial port modes that allow variable baud rates, this baud rate is set by timer 1.
The RS232 connector was originally developed to use 25 pins. In this DB25 connector pinout provisions were made for a secondary serial RS232 communication channel. In practice, only one serial communication channel with accompanying handshaking is present. Only very few computers have been manufactured where both serial RS232 channels are implemented. Examples of this are the Sun SparcStation 10 and 20 models and the Dec Alpha Multia. Also on a number of Telebit modem models the secondary channel is present. It can be used to query the modem status while the modem is on-line and busy communicating. On personal computers, the smaller DB9 version is more commonly used today. The diagrams show the signals common to both connector types in black. The defined pins only present on the larger connector are shown in red. Note, that the protective ground is assigned to a pin at the large connector where the connector outside is used for that purpose with the DB9 connector version.
The DB9 (originally DE-9) connector is an analog 9-pin plug of the D-Subminiature connector family (D-Sub or Sub-D).
The DB9 connector is mainly used for serial connections, allowing for the asynchronous transmission of data as provided for by standard RS-232 (RS-232C).
The only thing left is that we need some sort of connector to connect to the serial port. The sample code below is written for Comm1 and most computers use a 9 pin DB9 male connector for Comm1 so a 9 pin female connector is included for this project. We also need a DB9 extension cable to make the connection easier. There should be 3 wires soldered to the DB9 connector pins 2, 3 and 5. Connect the wire from pin 5 of the connector to ground on the breadboard. Connect the wire from pin 2 of the connector to pin 14 of the MAX232.
DB9 pin connector for RS232 serial Communication between humidity monitoring project and computer.
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DB9 pin connector for RS232 serial Communication,db9 pinout,db9 connector,db9 cable,db9 price,db9 serial port,aston martin,rs232,db9 serial
rs232 db9 connector,db9 connector datasheet,db25 connector,outlook connector,keyboard with 9 pin d connector,mini din connector,db9 connector configuration,15 pin,Converts a USB port into a 9-pin male RS-232 serial port, DB9 Serial Cables, DB9 mice mouse cable Cables Serial Cable Computer Cables Computer Cable Switch Box USB Switch boxes Monitor Cables Assembly cables.Shop for DB9 Cable Cables and Connectors Computer Accessories and read product reviews. Find cheap prices on DB9 Cable Cables and Connectors Computer,Serial (RS232) null modem cable (DB9-DB9). Pinout and signals for building a serial (RS232) nullmodem cable. Use this cable between two DTE devices,RS232 serial cables and adapters. Pinout and wiring layout for many situations. DB9 to DB25 conversion and null modem wiring diagrams.This creates an electrically continuous screen covering the whole cable and connector ... It is now common to see DE9 connectors sold as "DB9" connectors.Cables To Go offers a wide selection of DB9 RS-232 Cables ready to ship today! Need help? Chat with one of our cable experts.
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