Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
437
Messaging Unit—Intel
®
81341 and 81342
4.9.12
MU Configuration Register - MUCR
The MU Configuration Register (MUCR) contains the Circular Queue Enable bit and the
size of one Circular Queue. The Circular Queue Enable bit enables or disables the
Circular Queues. The Circular Queues are disabled at reset to allow the software to
initialize the head and tail pointer registers before any PCI accesses to the Queue Ports.
Each Circular Queue may range from 4 K entries (16 Kbytes) to 64 K entries (256
Kbytes) and there are four Circular Queues.
This register also contains the upper four bits of the 36-bit QBR address. Local memory
is 36-bit addressable.
Table 276. MU Configuration Register - MUCR
Bit
Default
Description
31:20
000H
Reserved
19:16
0H
Upper Queue Base Address - These four bits contain the upper 4-bit address of the 36-bit QBR. Local
memory is 36-bit addressable.
15:06
000000H Reserved
05:01
00001
2
Circular Queue Size - This field determines the size of each Circular Queue. All four queues are the same
size.
• 00001
2
- 4K Entries (16 Kbytes)
• 00010
2
- 8K Entries (32 Kbytes)
• 00100
2
- 16K Entries (64 Kbytes)
• 01000
2
- 32K Entries (128 Kbytes)
• 10000
2
- 64K Entries (256 Kbytes)
00
0
2
Circular Queue Enable - This bit enables or disables the Circular Queues. When clear the Circular Queues
are disabled, however the MU accepts Host I/O Interface accesses to the Circular Queue Ports but
ignores the data for Writes and return FFFF.FFFFH for Reads. Interrupts are not generated to the core
when disabled. When set, the Circular Queues are fully enabled.
PCI
IOP
Attributes
Attributes
28
24
20
16
12
8
4
0
31
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rw
na
rw
na
rw
na
rw
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rw
na
rw
na
rw
na
rw
na
rw
na
rw
na
Attribute Legend:
RV = Reserved
PR = Preserved
RS = Read/Set
RW = Read/Write
RC = Read Clear
RO = Read Only
NA = Not Accessible
MUCR
internal bus address offset
4050H