From a hardware protocol perspective, the items of interest
deal with answering
questions such as:
What are the voltage values that define logic 1 or logic 0?
How many wires are needed?
Where are the connected and why?
From a firmware protocol perspective, the items of interest deal
with answering
questions that deal with the
configuration of the 8250 itself.
Some example questions
that become significant at this
point include:
How many Stop bits?
What is the baud rate?
What ( if any) is the Parity?
How many bits is the data character?
8250 Registers
8250 Transmitter & Receive Registers
Status and Interrupt Registers
8250 Divisor Latch
Baudrate
Modem Registers
From the software protocol view, the interest shifts to
the actual formate of the
data message. This leads to
questions
now include:
Is a data character an ASCII character?
( or Gray Code for example)
Are there any characters that surround the data message?
(coma's for example)?
7 Bit ASCII Code