UART tx delay
there is something I don't understand about the delay necessary for UART transmission.
A premise: working with PIC24FJ1024GB610, at 8 MHz Fosc, I have already verified that every single nop requires 250 ns (2 cycles), as expected.
Now, in the Microchip documentation:
- it is stated that before sending the first character it is necessary to wait at least (1 / baudrate) seconds: working at 9600 baud, this wait would be about 105 µs;
- the DELAY_105us example function provides for a wait corresponding to 4201 nop.
- in my tests the transmission delay must be applied before each character sent (not only before the first one);
- working at 8 MHz, 105 µs should be around 420 nop, not 10 times as much; however, if the delay is less than 4136 nop (in my tests), the transmissions fail.
So ... I missed something: why is it necessary to wait about 4200 nop (at least 4136) instead of 420 only?
Thank you for any suggestion.