Intel
®
81341 and 81342—Messaging Unit
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
418
Order Number: 315037-002US
Table 262. Circular Queue Summary
Queue Name
Host I/O
Interface Port
Generate Host I/
O Interface
Interrupt
Generate Intel
XScale
®
processor
Interrupt
Head Pointer
maintained by
Tail Pointer
maintained by
Inbound Post Queue
Inbound Queue Port
No
Yes, when queue is
written
MU hardware
Intel XScale
®
microarchitecture
Inbound Free
Queue
No
No
Intel XScale
®
microarchitecture
MU hardware
Outbound Post
Queue
Outbound Queue
Port
Yes, when data in
prefetch buffer is
valid
No
Intel XScale
®
microarchitecture
MU hardware
Outbound Free
Queue
No
Yes, when the
queue is full
MU hardware
Intel XScale
®
microarchitecture
Table 263. Circular Queue Status Summary
Queue Name
Queue Status
Head & Tail Pointer
Last Pointer Update
Inbound Post Queue
&
Outbound Free Queue
Empty
Equal
Tail pointer last updated by
software
a
Not Empty
Not Equal
N/A
Full
Equal
Head pointer last updated by
hardware
b
Inbound Free Queue
&
Outbound Post Queue
Empty
Equal
Tail pointer last updated by
hardware
c
Not Empty
Not Equal
Full
Equal
Head pointer last updated by
software
d
a. The Inbound Post Queue and Outbound Free Queue Tail Pointers are only managed by
software
respectively using the
“Inbound Post Tail Pointer Register - IPTPR”
and
during normal operation and initialization.
b. During normal operation, the Inbound Post Queue and Outbound Free Queue Head Pointers are
only managed by
hardware
.
Software
can also update the Head Pointers respectively using the
“Inbound Post Head Pointer Register - IPHPR”
and
“Outbound Free Head Pointer Register -
during initialization. However, the Inbound Post Queue and Outbound Free Queue logic
does not make a distinction on whether the Head Pointers are updated using hardware or
software.
c. During normal operation, the Inbound Free Queue and the Outbound Post Queue Tail Pointers are
only managed by
hardware
.
Software
can also update the Tail Pointers respectively using the
“Inbound Free Tail Pointer Register - IFTPR”
and
“Outbound Post Tail Pointer Register - OPTPR”
during initialization. However, the Inbound Free Queue and Outbound Post Queue logic does not
make a distinction on whether the Tail Pointers are updated using hardware or software.
d. The Inbound Free Queue and the Outbound Post Queue Head Pointers are only managed by
software
respectively using the
“Inbound Free Head Pointer Register - IFHPR”