Intel 386

Intel386™ EX EMBEDDED MICROPROCESSOR USER’S MANUAL
11-8
Figure 11-4. SIO n Data Transmission Process Flow
A2527-02
Select the BCLKIN source and
the transmitter input baud rate.
Select the data frame. (Word length, number
of stop bits, and type of parity.) Enable interrupts
and/or DMA.
Is
transmit buffer
empty?
Write data to transmit buffer register.
(ISR or DMA cycle)
Transmitter shifts data frame onto
the TXD
n pin. Data is transmitted
least-significant bit first.

Transmitter transfers data to shift register
and sets transmit buffer empty flag, causing
an interrupt or DMA request.
End
Yes
No
Transmitter shifts out last stop bit 
then sets the transmitter empty flag.
More
Data to
Transmit
?
No
Yes