Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
153
Address Translation Unit (PCI-X)—Intel
®
81341 and 81342
2.13.5
ATU Command Register - ATUCMD
ATU Command Register bits adhere to the definitions in the PCI Local Bus Specification,
Revision 2.3 and in most cases, affect the behavior of the PCI ATU and devices on the
PCI bus.
Table 27. ATU Command Register - ATUCMD
Bit
Default
Description
15:11
00000
2
Reserved
10
0
2
Interrupt Disable - Setting this bit disables the ATU function of 81341 and 81342 from asserting the
INT[A:D]#
signals. Clearing this bit enables the assertion of the
INT[A:D]#
signals by the ATU
function of 81341 and 81342.
09
0
2
Fast Back to Back Enable - When cleared, the ATU interface is not allowed to generate fast back-to-back
cycles on its bus. Ignored when operating in the PCI-X mode.
08
0
2
SERR#
Enable - When cleared, the ATU interface is not allowed to assert
SERR#
on the PCI interface.
07
0
2
Hard-wired 0
06
0
2
Parity Error Response - When set, the ATU takes normal action when a parity (or uncorrectable ECC)
error is detected. When cleared, parity (or uncorrectable ECC) checking is disabled.
Note:
When the bit is cleared in PCI-X Mode 2, the 81341 and 81342 records all ECC errors in the ECC
Control and Status, ECC First Address, ECC Second Address, and ECC Attribute registers but in
all other respects treats the transaction as though it had no error. Correctable ECC errors are
corrected independent of the state of this bit.
05
0
2
VGA Palette Snoop Enable - The ATU interface does not support I/O writes and therefore, does not
perform VGA palette snooping.
04
0
2
Memory Write and Invalidate Enable - When set, ATU may generate MWI commands. When clear, ATU
use Memory Write commands instead of MWI. Ignored when operating in the PCI-X mode.
03
0
2
Special Cycle Enable - The ATU interface does not respond to special cycle commands in any way. Not
implemented and a reserved bit field.
02
0
2
Bus Master Enable - The ATU interface can act as a master on the PCI bus. When cleared, disables the
device from generating PCI accesses. When set, allows the device to behave as a PCI bus master.
When operating in the PCI-X mode, ATU initiates a split completion transaction regardless of the state of
this bit.
01
0
2
Memory Enable - Controls the ATU interface’s response to PCI memory addresses. When cleared, the
ATU interface does not respond to any memory access on the PCI bus.
00
0
2
I/O Space Enable - Controls the ATU interface response to I/O transactions.
The ATU does not support I/O transactions. This bit is Read Only.
PCI
IOP
Attributes
Attributes
15
12
8
4
0
rv
rv
rv
rv
rv
rv
rv
rv
rv
rv
rw
rw
rw
rw
rw
rw
ro
ro
rw
rw
ro
ro
rw
rw
ro
ro
rw
rw
rw
rw
ro
ro
Attribute Legend:
RV = Reserved
PR = Preserved
RS = Read/Set
RW = Read/Write
RC = Read Clear
RO = Read Only
NA = Not Accessible
Register Offset
+004H