Intel Extensible Firmware Interface, Спецификация

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Extensible Firmware Interface Specification
216 12/12/00 Version 1.02
The default attributes for all UART-style serial device interfaces are: 115,200 baud, a 1 byte
receive FIFO, a 1,000,000 microsecond timeout per character, no parity, 8 data bits, and 1 stop bit.
Flow control is the responsibility of the software that uses the protocol. Hardware flow control can
be implemented through the use of the
GetControl()
and
SetControl()
functions
(described below) to monitor and assert the flow control signals. The XON/XOFF flow control
algorithm can be implemented in software by inserting XON and XOFF characters into the serial
data stream as required.
Special care must be taken if a significant amount of data is going to be read from a serial device.
Since EFI drivers are polled mode drivers, characters received on a serial device might be missed.
It is the responsibility of the software that uses the protocol to check for new data often enough to
guarantee that no characters will be missed. The required polling frequency depends on the baud
rate of the connection and the depth of the receive FIFO.