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Thursday, 27 October 2011

Port Serial

serial port

Port Serial
Standard RS 232 was established by Electronic Industry Association and Telecommunication Industry Association in 1962. The complete name is EIA/TIA-232 interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange. In spite of its long name, this standard only relates to data communication between computers with computer complement equipment. There are two main stuffs set by standard RS 232, i.e:
Ø  Signal form and tension level used RS 232 was created in 1962, before ICTTL was well-known. Moreover, the tension level determined for RS 232 does not have any relation with the level TTL, even it is said that it is different. Here are differences between the tension level RS 232 and TTL:
Picture. Differences between the Tension Level RS232 and TTL
Ø  Determination of signal types and connector used, and signal structure in connector foot 9. Some parameters determined by EIA (Electronic Industry Association) are
1.      Space (logic 0) tension from +3 V to +25 V
2.      Mark (logic 1) tension from -3 V to -25 V
3.      Tension area from +3 to -3 V is not defined
4.      Open series tension must not more than 25 V (ground reference)
5.      Short connective series current must not more than 500 Ma
A driver has to be able to handle this current without getting broken. Beside describing the tension level like what it has been discussed above, Standard RS232 determines signal types used to arrange information exchange between DTE and DCE.
There are 24 signal types. However, common signal used are usually 9 signal types. Connector used is determined in standard RS 232, for complete signal used by connector DB 25. While connector DB 9 is only used for 9 signals which is commonly used

Transmit Data
For sending serial data
Received Data
For receiving serial data
Request to Send
A signal for informing modem that UART is ready to conduct data exchange
Clear to Send
Telling that modem is ready to conduct data exchange
Data Set Ready
For telling UART that modem is ready to conduct data exchange
Carrier Detect
While modem detect “carrier” from other modem, the signal will be activated
Data Terminal
The opposite of DSR, it is used for telling that UART is ready to conduct communication
For telling that UART is ready to conduct communication
Ring Indicator
It will be active if modem detects quivering signal from phone channel

Those signals 96 are in the direction of DCE and come from DCE. For the signals in the direction of DCE, it means that DTE has function as output and input, for example signal TxD, at the side of foot DTE TxD is output. This foot is connected to foot TxD on DCE which has a function as input. The other way around of TxD signal is RxD. This signal comes from DCE and it is connected to RxD foot on DTE which has a function as output.
Testing conducted by connecting two computers through port serial (port DB 9) is with null modem configuration. Null modem configuration is conducted with 3 data channel: TxD (sending channel), RxD (receiving channel), and ground.

Basically, serial communication inter PC occurs through port serial or DB9. Powerful component which can be used for accessing/serial communication for Delphi is comport. In creating the application of serial communication between two personal computers (PC), it needs two applications, i.e: data sender application and data receiver application. The application that will be created recently is simple application which can be then developed to be more complex application.

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