Programmed I/O - Transfers from the FIFO to
the Host
Programmed I/O - Transfers from the Host to
the FIFO
In the reverse direction an interrupt occurs when
serviceIntr is 0 and readIntrThreshold bytes are
available in the FIFO. If at this time the FIFO is
full it can be emptied completely in a single
burst, otherwise readIntrThreshold bytes may
be read from the FIFO in a single burst.
In the forward direction an interrupt occurs when
serviceIntr is 0 and there are writeIntrThreshold
or more bytes free in the FIFO. At this time if
the FIFO is empty it can be filled with a single
burst before the empty bit needs to be re-read.
Otherwise
it
may
be
filled
with
writeIntrThreshold bytes.
readIntrThreshold =(16-<threshold>) data bytes
in FIFO
writeIntrThreshold = (16-<threshold>)
bytes in FIFO
free
An interrupt is generated when serviceIntr is 0
and the number of bytes in the FIFO is greater
than or equal to (16-<threshold>). (If the
An interrupt is generated when serviceIntr is 0
and the number of bytes in the FIFO is less than
or equal to <threshold>. (If the threshold = 12,
then the interrupt is set whenever there are 12 or
less bytes of data in the FIFO.) The PINT pin
can be used for interrupt-driven systems. The
host must respond to the request by writing data
to the FIFO. If at this time the FIFO is empty, it
can be completely filled in a single burst,
otherwise a minimum of (16-<threshold>) bytes
may be written to the FIFO in a single burst.
This process is repeated until the last byte is
transferred into the FIFO.
threshold
= 12, then the interrupt is set
whenever there are 4-16 bytes in the FIFO).
The PINT pin can be used for interrupt-driven
systems. The host must respond to the request
by reading data from the FIFO. This process is
repeated until the last byte is transferred out of
the FIFO. If at this time the FIFO is full, it can
be completely emptied in
a single burst,
otherwise a minimum of (16-<threshold>) bytes
may be read from the FIFO in a single burst.
108
SMSC [ SMSC CORPORATION ]
