Geode™ CS4210
4.4.22 Asynchronous Request Filter Registers
The CS4210 allows for selective access to host memory
and the Asynchronous Receive Request context so that
software can maintain host memory integrity. The selective
access is provided by two sets of registers: PhysRequest-
Filter and AsyncRequestFilter. These registers allow
access to physical memory and the AR Request context on
a nodeID basis. The request filters are not applied to qua-
dlet read requests directed at the Config ROM (including
the ConfigROM header, BusID, Bus Options, and Global
Unique ID registers) nor to accesses directed to the isoch-
ronous resource management registers. When the link is
enabled, access by any node to the first 1K of CSR config
ROM is enabled (see Section 4.4.5 "Configuration ROM
Filters do not have any effect on Asynchronous Response
packets. When a request is received by the CS4210 from
the 1394 bus and that request does not access the first 1K
of CSR config ROM on the CS4210, then the sourceID is
used to index into the AsyncRequestFilter. If the corre-
sponding bit in the AsyncRequestFilter is set to 0, then
requests from that device are not enabled; there is no ack_
sent, and the requests are ignored by the CS4210. If, how-
ever, the bit is set to 1, the requests are accepted and pro-
cessed according to the address of the request and the
setting of the PhysicalRequestFilter register (BAR0+Offset
110h, see Section 4.4.23 "Physical Request Filter Regis-
0000_FFFF_FFFFh, with the exception of offsets handled
physically as described in Section 3.6 "Physical Requests"
Receive DMA context. If the AR Request DMA context is
not enabled, then the CS4210 ignores the request. These
registers are set and clear. If bit asyncReqResourceN is
set, then requests with a sourceID of either {3FFh, #N} or
{busID, #N} are accepted. If the asyncReqResourceAll bit
is set in AsyncRequestFilterHi, requests from all bus nodes
including those on the local bus are accepted. Reading the
AsyncRequestFilter registers returns their current state. All
asyncReqResourceN bits in the AsyncRequestFilter regis-
ter are cleared to 0 on a 1394 bus reset.
Table 4-37. BAR0+Offset 100h (Set) and 104h (Clear): AsyncRequestFilterHi Register
Bit
31
Name
asyncReqRe-
sourceAll
Access
RSCU
Reset
0
Description
Asynchronous Requests Resource All:
If set to one, all asynchronous
requests received by the CS4210 from all bus nodes (including the local
bus) are accepted, and the values of all asyncReqResourceN bits are
ignored. A bus reset does not affect the value of the asyncReqResourceAll
bit.
Asynchronous Requests Resource [62:32]:
If set to one for local bus
node number N, asynchronous requests received by the CS4210 from that
node are accepted. All asyncReqResourceN bits are cleared to zero when
a bus reset occurs.
30:0
asyncReqRe-
sourceN
RSCU
00h
Table 4-38. BAR0+Offset 108h (Set) and 10Ch (Clear): AsyncRequestFilterLo Register
Bit
31:0
Name
asyncReqRe-
sourceN
Access
RSCU
Reset
00h
Description
Asynchronous Requests Resource [31:0]:
If set to one for local bus node
number N, asynchronous requests received by the CS4210 from that node
are accepted. All asyncReqResourceN bits are cleared to zero when a bus
reset occurs.
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