First introduce some concepts.
Start bit: issuing a first logic "0" signal, indicating the start of data transmission.
Parity: After this data bits plus one, so that the number of bits "1" should be an even (even parity) or odd (odd parity), in order to verify the correctness of the data transfer. For example, on transport "A" (01000001), for example. (The character 'A' is binary 01000001)
When the parity is odd: bit 8-bit character "A" in a two, then the parity bit is to meet a number of 1 is an odd number (odd parity).
When the even parity is: bit 8-bit character "A" in a two, then the parity bit is 0 in order to meet a number is even (even parity).
This bit can also be removed, ie without parity bits.
Stop bits: it is an end marker data. It can be a 1bit, 1.5bit, idle level of 2bit. Perhaps I find it very strange how there will be 1.5 ~ Yes, indeed there. So I uart in the production of this signal waveform with two points to represent a bit. This may not necessarily get to the bottom. . .
Idle bit: no level state on the line when transmitting data. A logic 1.
Transmission direction: the data transfer is started from the high (MSB) or start transmission from the low (LSB). Such transfer "A" (the character 'A' is binary 01000001)
If the MSB is then 01000001 (FIG. -2), so that if LSB 10000010
Uart transmission data sequence is: the beginning of a start bit transmitted - the transmission of data bits - parity bit (this bit may not be required) - the stop bit.
Such a data transmission on finished. Next then transported up like this. Here also like to say a parameter.
Frame interval: the transfer size of the interval between the data frame to frame, the bit may also be used as the metering time (known baud rate and the number of bits that can be converted to time). Such transfer "A" finished, which is a data re-transmission "B", then the interval between A and B is, inter
experiment:
With serial transmission 0XD6 tool, i.e. two system 11,010,110, thus displayed on the oscilloscope.
Serial port settings: 9600 baud, 1 stop bit, no parity.
On an oscilloscope, a low level indicates the leftmost 0, the start bit; followed is 01101011, and just the most significant bit and least significant bit of data transmitted in turn. As shown below.
This is called the LSB.
________ transmission direction: the data transmission is started or high (MSB) starts from the transmission from the low (LSB)
Again example: 0x75 serial port transmission is binary 01110101, as shown below.
Serial port settings: 9600 baud, 1 stop bit, no parity.
Similarly, starting from the leftmost bit, low level 0, then the transmission LSB. 10101110 sequentially transmitted to the oscilloscope.
Third Example: 0x75 serial transmission, is binary 01110101,
Serial port settings: 9600 baud, 1 stop bit, odd parity.
Odd parity is to ensure that all of the frames in the BIT have an odd number, 0x75 has 5 1, so the parity bit is 0 can be. As shown below.
Similarly, if even parity, then the last bit should be a high level 1, there will be 6 1, in order to ensure that all of the number 1 is even.
Finally, two bursts transmitted hexadecimal data 0x75 (0111 0101) 0x6B (0110 1011)
Serial port settings: 9600 baud, 1 stop bit, no parity.
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