| ??? 10/11/08 20:23 Modified: 10/11/08 20:29 Read: times |
#158982 - 805x Mode 0 is not asynchronous Responding to: ???'s previous message |
The Mode 0 offered by most 805x types is a bit-synchronous mode, half-duplex only, and not capable of "normal" synchronous communication either. It is very much like the keyboard protocol used by most PC keyboards, though, in that it produces clock synchronized to the data rate, but it produces neither start or stop bits. If your 805x waits for the TI bit before loading SBUF with the next character there will be considerably more than a bit time during which the line is idle, in most cases, as it clocks the shift register at X1/12 in most cases.
the bible said: Mode 0: Serial data enters and exits through RxD. TxD outputs the shift clock. 8 bits are transmitted/received (LSB first). The baud rate is fixed at 1/12 the oscillator frequency... ...As data bits shift out to the right, zeros come in from the left. When the MSB of the data byte is at the output position of the shift register, then the 1 that was initially loaded into the 9th position, is just to the left of the MSB, and all positions to the left of that contain zeros. This condition flags the TX Control block to do one last shift and then deactivate SEND and set T1. Both of these actions occur at S1P1 of the 10th machine cycle after “write to SBUF.” You can see from this that it would be tricky to time write to SBUF such that it would behave compatibly with truly synchronous devices. Few other architectures support this particular mode of communication. RE |
| Topic | Author | Date |
| UART0 - Mode 0 of LPC2148 | 01/01/70 00:00 | |
| What mode 0 | 01/01/70 00:00 | |
| What does the datasheet say? | 01/01/70 00:00 | |
| 805x Mode 0 is not asynchronous | 01/01/70 00:00 | |
| Like I said to your duplicate posting... | 01/01/70 00:00 | |
not to mention ... | 01/01/70 00:00 |