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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—AHB Queue Manager
(AQM)
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
934
Reference Number: 306262-004US
27.4.2.2
Status Interrupts
Two processor interrupts will be provided, one for queues 0-31 and one for queues 32-
63. Each of the interrupt signals is computed as a masked 32-way logical-OR of one
edge-sensitive status bit per queue. In other words, each queue contributes a single
edge-sensitive input into one of the 32-way logical-OR combinations. For queues 0-31,
this input is independently configurable. It may be a positive or negative edge-sensitive
version of any one of the E, NE, NF or F status flag bits. The selected status flag may be
different for each queue. For queues 32-63, the input is always the NE status flag bit
with a positive edge-sensitive version only. The set of selected 32 condition signals is
masked by the corresponding interrupt enable register but the value of
INT0SRCSELREG0 bit 3 affects how this happens in a subtle way.
There is a bit in INT0SRCSELREG0 which will modify the reset operation of the
interrupts. If bit 3 of this register is set to 0, then these interrupts are generated for
active high, level triggered usage. On occurrence of the selected transition of one or
more of the status flag sources, an active high interrupt level is registered. Via the
AHB, the processor can read a 32-bit Interrupt register to determine the source or
sources for each interrupt. Selective interrupt reset capability will be provided for each
of the queue sources via writing a one to the appropriate queue bit(s) within the
interrupt register. Upon clearing (i.e. writing a ‘1’ to) the appropriate bit(s) in the
Interrupt Register, the interrupt cannot be generated again by the same source, until
the active status flag condition is removed and then are asserted again. If the interrupt
is reset, but the condition is still active, the interrupt register will not reflect the status.
In this mode, the interrupt enable register affects whether or not the bit may be set,
and the interrupt is simply the logical ‘OR’ of the interrupt register.
Table 294.
Queue Status Flags
Nearly Empty
Watermark
Nearly Full
Watermark
# Entries in the
Queue
E
NE
NF
F
0 (000)
0 (000)
0
1 – 63
64
1
0
0
1
0
0
0
0
1
0
0
1
1 (001)
1 (001)
0
1
2 – 62
63
64
1
0
0
0
0
1
1
0
0
0
0
0
0
1
1
0
0
0
0
1
2 (010)
2 (010)
0
1 – 2
3 - 61
62 – 63
64
1
0
0
0
0
1
1
0
0
0
0
0
0
1
1
0
0
0
0
1
4 (011)
4 (011)
0
1 – 4
5 – 59
60- 63
64
1
0
0
0
0
1
1
0
0
0
0
0
0
1
1
0
0
0
0
1
8 (100)
8 (100)
0
1 - 8
9 – 55
56 - 63
64
1
0
0
0
0
1
1
0
0
0
0
0
0
1
1
0
0
0
0
1