Altera Embedded Peripherals IP Uživatelský manuál Strana 165

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Bit(s) Name Description
5 UNDERFLOW Is set to 1 for 1 cycle every time the FIFO underflows. The FIFO
underflows when an Avalon read master reads from an empty FIFO.
UNDERFLOW is only valid when Allow backpressure is off.
These fields are identical to those in the status register and are set at the same time; however, these fields
are only cleared when software writes a one to clear (W1C). The event fields can be used to determine if a
particular event has occurred.
Table 16-6: Event Bit Field Descriptions
Bit(s) Name Description
1 E_FULL Has a value of 1 if the FIFO has been full and the bit has not been
cleared by software.
0 E_EMPTY Has a value of 1 if the FIFO has been empty and the bit has not been
cleared by software.
3 E_ALMOSTFULL Has a value of 1 if the fill level of the FIFO has been greater than the
almostfull threshold value and the bit has not been cleared by
software.
2 E_ALMOSTEMPTY Has a value of 1 if the fill level of the FIFO has been less than the
almostempty value and the bit has not been cleared by software.
4 E_OVERFLOW Has a value of 1 if the FIFO has overflowed and the bit has not been
cleared by software.
5 E_UNDERFLOW Has a value of 1 if the FIFO has underflowed and the bit has not been
cleared by software.
The table below provides a mask for the six STATUS fields. When a bit in the event register transitions
from a zero to a one, and the corresponding bit in the interruptenable register is set, the master is
interrupted.
Table 16-7: InterruptEnable Bit Field Descriptions
Bit(s) Name Description
1 IE_FULL Enables an interrupt if the FIFO is currently full.
0 IE_EMPTY Enables an interrupt if the FIFO is currently empty.
3 IE_ALMOSTFULL Enables an interrupt if the fill level of the FIFO is greater than the
value of the almostfull register.
2 IE_ALMOSTEMPTY Enables an interrupt if the fill level of the FIFO is less than the value of
the almostempty register.
4 IE_OVERFLOW Enables an interrupt if the FIFO overflows. The FIFO overflows when
an Avalon write master writes to a full FIFO.
5 IE_UNDERFLOW Enables an interrupt if the FIFO underflows. The FIFO underflows
when an Avalon read master reads from an empty FIFO.
6 ALL Enables all 6 status conditions to interrupt.
16-10
Software Control
UG-01085
2014.24.07
Altera Corporation
On-Chip FIFO Memory Core
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