| ??? 12/30/05 03:09 Read: times |
#106211 - So true! Responding to: ???'s previous message |
Dan Henry said:
Just as in non Bit-Bang comms, it depends on all aspects of the signaling means (e.g., data rate, medium, environment, etc.).
EDIT: ... and all those aspects/factors being the same, there would not be any difference between Bit-Bang and normal comms endpoint separation. Very well stated! Perhaps the most important part is "all those aspects/factors being the same". It is an all-inclusive statement, not to be taken lightly. This goes well beyond obvious things like cables, connectors, drivers, and so on. Consider, for example, this excerpt describing the operation of the 8051's serial port in mode 1: 80C51 family hardware description said:
The 16 states of the counter divide each bit time into 16ths. At the 7th, 8th, and 9th counter states of each bit time, the bit detector samples the value of RxD. The value accepted is the value that was seen in at least 2 of the 3 samples. This is done for noise rejection. If the value accepted during the first bit time is not 0, the receive circuits are reset and the unit goes back to looking for another 1-to-0 transition. This is to provide rejection of false start bits. If the start bit proves valid, it is shifted into the input shift register, and reception of the rest of the frame will proceed. Thus, if you wanted to bit bang an additional serial port (not that I suggest this) with identical reception characteristics to its hardware counterpart, you would have to sample the incoming data 3 times per bit (near the temporal center of the bit) and take a majority vote. If you want your bit-banged interface to really perform, you're going to have to work at it. --Sasha Jevtic |
| Topic | Author | Date |
| Bit-Bang connect | 01/01/70 00:00 | |
| Same-same | 01/01/70 00:00 | |
| So true! | 01/01/70 00:00 | |
value of oversampling | 01/01/70 00:00 |