Achronix ACE Version 5.0 User Manual
Page 83
Editors
Chapter 3. Concepts
Almost Full Offset
(decimal)
This defines the word depth at which the FIFO
almost full
signal
is asserted. The
almost full
flag is asserted when there are
(afull offset + 1) or fewer locations available to be written in the
FIFO. The
almost full
signal is asserted when the the difference
between the Write Pointer and the Read Pointer is greater than or
equal to the difference between the Maximum FIFO Depth and the
value of this field (afull offset parameter).
Almost Empty
Offset (decimal)
This defines the word depth at which the FIFO
almost empty
signal is asserted. The
almost empty
flag is asserted when there
are (aempty offset - 1) or fewer words remaining in the FIFO. The
almost empty
signal is asserted when the the difference between
the Write Pointer and the Read Pointer is less than the value of this
field (aempty offset parameter).
First Word Fall Through Enabled
When enabled, the first value written into the FIFO appears at the
dout
output without having to perform a read operation. If First
Word Fall Through is disabled, the first data word written into the
FIFO is available at the FIFO output one
rdclk
clock cycle after the
first read operation. This parameter only affects the availability of
the first word written into the FIFO after an empty condition.
Operation of the two modes is the same after the first read operation
is performed.
Synchronized Reset Mode
When this is disabled, both the read and write pointers resets utilize
the Reset Synchronizer circuitry. When this option is enabled the
rstn
input must be synchronous to the
wrclk
/
rdclk
clock
driving the FIFO.
Prevent Overflow/Underflow
Enabling this option allows the user to read from the FIFO when the
FIFO is empty and write to the FIFO when it is full. Disabling this
safety check will allow the FIFO to run faster. Details can be found
in the user macro guide.
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UG001 Rev. 5.0 - 5th December 2012