M1AFS600-PQ208 Datasheet, PDF (89/334 Pages) Microsemi Corporation – Fusion Family of Mixed Signal FPGAs

Fusion Family of Mixed Signal FPGAs
FSTOP is used to stop the FIFO write counter from further counting once the FIFO is full (i.e., the FULL
flag goes High). A High on this signal inhibits the counting.
For more information on these signals, refer to the "ESTOP and FSTOP Usage" section on page 2-73.
FULL, EMPTY
When the FIFO is full and no more data can be written, the FULL flag asserts High. The FULL flag is
synchronous to WCLK to inhibit writing immediately upon detection of a full condition and to prevent
overflows. Since the write address is compared to a resynchronized (and thus time-delayed) version of
the read address, the FULL flag will remain asserted until two WCLK active edges after a read operation
eliminates the full condition.
When the FIFO is empty and no more data can be read, the EMPTY flag asserts High. The EMPTY flag
is synchronous to RCLK to inhibit reading immediately upon detection of an empty condition and to
prevent underflows. Since the read address is compared to a resynchronized (and thus time-delayed)
version of the write address, the EMPTY flag will remain asserted until two RCLK active edges after a
write operation removes the empty condition.
For more information on these signals, refer to the "FIFO Flag Usage Considerations" section on
page 2-74.
AFULL, AEMPTY
These are programmable flags and will be asserted on the threshold specified by AFVAL and AEVAL,
respectively.
When the number of words stored in the FIFO reaches the amount specified by AEVAL while reading,
the AEMPTY output will go High. Likewise, when the number of words stored in the FIFO reaches the
amount specified by AFVAL while writing, the AFULL output will go High.
AFVAL, AEVAL
The AEVAL and AFVAL pins are used to specify the almost-empty and almost-full threshold values,
respectively. They are 12-bit signals. For more information on these signals, refer to "FIFO Flag
Usage Considerations" section.
ESTOP and FSTOP Usage
The ESTOP pin is used to stop the read counter from counting any further once the FIFO is empty (i.e.,
the EMPTY flag goes High). Likewise, the FSTOP pin is used to stop the write counter from counting any
further once the FIFO is full (i.e., the FULL flag goes High).
The FIFO counters in the Fusion device start the count at 0, reach the maximum depth for the
configuration (e.g., 511 for a 512×9 configuration), and then restart at 0. An example application for the
ESTOP, where the read counter keeps counting, would be writing to the FIFO once and reading the same
content over and over without doing another write.
Revision 4
2- 73