[Lazarus] SdpoSerial Tx and Rx buffers?

[José Mejuto]

Hello Lazarus-List,

Thursday, February 17, 2011, 12:25:26 AM, you wrote:

>> AFAIK the FIFO is in the receive, in sent the FIFOs are filled but
>> function does not return until the hardware sends the last byte.

HPD> I'm not sure, but IMO a FIFO for outgoing data is used at best in a
HPD> *synchronous* protocol, not in a UART. More likely synchronous I/O is
HPD> done by DMA, not in code. But which nowadays hardware is capable of
HPD> synchronous serial transmission at all?

Now you know why PCSpeaker has been removed from Windows ;) 8250 chip
which carries RS232 has been removed and it also controls the
PCSpeaker. The 8250 is interrupt driven without FIFO and the 16550A is
interrupt driven and FIFO 16 bytes.
16550A and alike are no more integrated in PC motherboards because it
is the last real IRQ and port mapped device so it overcomplex
circuitry and OS to handle it. Anyway the APIs are based in the same
concept as when it was interrupt and I/O driven (around 3 years ago).

Of course the 16550A chip was not included since a lot of years, but
the circuitry in replacement was compatible in operation mode
(IRQs / I/O).

-- 
Best regards,
 José