it just needs setting the parameters (start bit ,baud rate, the parity,stop bit, check sum)
YesWhat is check sum?
it just needs setting the parameters (start bit ,baud rate, the parity,stop bit, check sum)
Hello
no thing else in DB9 pins are used in UART because UART means (universal Asynchronous receive transmission) it just needs setting the parameters (start bit ,baud rate, the parity,stop bit, check sum)
kamal
Yes
Many serial protocols use checksum (additional bytes added at the end of the data string) to check the data integrity, as errors might occur during data transmission. There are many types of checksum, from the simplest uses
it is used in UASRT communication RS232 protocol but neglected in UART
kamal
Going back to post #1 - ALL the pins have a function, it is already a sub-set of DB25 to eliminate non-essential signals. There are many references to the pin usage on the internet.
It is true that a minimal serial link can be established with only TX, RX and GND but that assumes software handshaking is used and no 'alert' (RI) signal is needed. The other signals are to announce the devices are ready to communicate and to allow or suspend the data flow.
The CRC is an entirely software issue. It is an accumulation of the data bytes fed through a polynomial equation to produce a checksum which is then transmitted after the data. The receiving device also carries out the calculation and if the two numbers don't match it flags an error has occurred.
Brian.
The wiki pages on UART and RS 232 spell out the difference in the first paragraph.One more question, how UART is differ from RS 232 ? Are they same terms or have different meanings ?
checksum byte(s) is neglected like parity bit. parity by default is "non"(no even and neither odd) checksum is bytes (two byte) is sent at the end of the data string as in the" RTU mode" and "ASCII mode" protocol. which is called "CRC CHECK" instead of including it "checksum " with UART techniques. which chip includes check sum byte(s)?Checksum is not in the list of parameters to be configured in the control byte - but that depends on the chip used.
Yes in total only three pins, i.e, 2, 3 and 5 are used when your device supports UART techniques (that means your device(MCU) has a built -in UART)This was my original question, is it possible to implement complete UART protocol (start bit ,baud rate, the parity,stop bit, check sum) with only pin 2 (Rx), 3 (Tx) and 5 (GND) in DB 9 connector ? If yes then I guess the DB 9 connector can also be used for other protocol as well, for example RS-485 that uses only pin 8 and pin 9.
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The checksum (additional bytes that added at the end of the data string for data integrity) has also to be sent through pin 2 (Rx), pin 3 (Tx) and there is no other pin other then pin 5 (GND) that we need to use to implement UART, right ? In total only three pins, i.e, 2, 3 and 5
checksum byte(s) is neglected like parity bit. parity by default is "non"(no even and neither odd) checksum is bytes (two byte) is sent at the end of the data string as in the" RTU mode" and "ASCII mode" protocol. which is called "CRC CHECK" instead of including it "checksum " with UART techniques. which chip includes check sum byte(s)?
Barry explained software handshaking in post #11, it send specific codes along the data path to stop and resume the data flow. The obvious drawback to that is those codes may be part of the actual data so further protection against false handshaking may be needed. They are added to the data as it is sent so it can cause other problems it makes the data block bigger than anticipated.
Barry explained software handshaking in post #11, it send specific codes along the data path to stop and resume the data flow. The obvious drawback to that is those codes may be part of the actual data so further protection against false handshaking may be needed. They are added to the data as it is sent so it can cause other problems it makes the data block bigger than anticipated.
YES (start bit ,baud rate, data length (7,or 8 bit ) stop bit ) are in the controller setting that has (USART-bult-in function ) many manufactured controllers comes with already setting (8 bit data length) so the setting get short only (start ,baud,stop) regarding checksum byte(s). there is no dependant(no setting) of checksum on the chip. the checksum mainly used in ASCII mode and RTU mode protocolRight.
The settings are in the controller, no of bits, start bit, parity stop bit etc are in the controller and not set by the pins.
Yes, XON/XOFF can be used (widely used but good for text strings) as software control instead of data set ready / data terminal ready that are hardware signals implemented via signal pins.
In the early days, these were widely used with telephone modems (pin 9 in DB9 shell is called RING INDICATOR) and almost all the pins were needed. But I have not seen all the 25 pins being used in D connector with 25 pins). High speed communication is very difficult with software XON/XOFF.
I can see no pin (indeed you mean"signal") in RS232 that can check "accuracy".1 pin for announcing, and the rest for handling and checking the accuracy of the data.
MODBUS and PROFIBUS are widely used in industry. They don't use handshake pins.On the other hand, almost all industrial equipment uses handshake pins.
It is an UART signal (not directly related to RS232), but surely it is no "pin".
RS232 does not include "validity checks".
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