Intel
®
81341 and 81342—Messaging Unit
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
438
Order Number: 315037-002US
4.9.13
Queue Base Address Register - QBAR
The Queue Base Address Register (QBAR) contains the lower 32-bit of the 36-bit local
memory address of the Circular Queues. The base address is required to be located on
a 1 Mbyte address boundary. The upper four-bits of the QBR is located in the MU
Configuration Register (MUCR).
All Circular Queue head and tail pointers are based on the QBAR. When the head and
tail pointer registers are read, the Queue Base Address is returned in the upper 12 bits.
Writing to the upper 12 bits of the head and tail pointer registers does not affect the
Queue Base Address or Queue Base Address Register.
Warning:
The QBAR must designate a range allocated to the 81341 and 81342’s DDR SDRAM
interface (
Chapter 7.0, “DDR SDRAM Memory Controller”
).
Table 277. Queue Base Address Register - QBAR
Bit
Default
Description
31:20
000H
Queue Base Address - Local memory address of the circular queues.
19:00
00000H
Reserved
PCI
IOP
Attributes
Attributes
28
24
20
16
12
8
4
0
31
rw
na
rw
na
rw
na
rw
na
rw
na
rw
na
rw
na
rw
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
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
Attribute Legend:
RV = Reserved
PR = Preserved
RS = Read/Set
RW = Read/Write
RC = Read Clear
RO = Read Only
NA = Not Accessible
QBAR
internal bus address offset
4054H