AFS090 datasheet(89/334 Pages) MICROSEMI

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Fusion Family of Mixed Signal FPGAs

R e visio n 2

2 - 73

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.

AFS090 数据表(PDF) 89 Page - Microsemi Corporation

AFS090 数据表(HTML) 89 Page - Microsemi Corporation

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