Specifications

6-46 I/O Port
Table 6-19 Sparse Window Read Command Packet Description
Sparse Window Write Command Packet
The Sparse Window Write command packet is used by processors to write
control and status registers in adapters on remote I/O buses that support
direct I/O window space.
A Sparse Window Write command packet must be acknowledged by a Win-
dow Write Status Return packet to the I/O port on the Up Hose. This
packet is supported by the I/O Window, Full, and Memory Channel vari-
ants of the hose protocol.
Figure 6-19 shows the Sparse Window Write Command packet.
Field Description
Clock 1, <31:30>
Are always zero.
Clock 1, <29:26>
Virtual ID of the TLSB commanding node. The VID indicates which CPU
is requesting the data. The VID is returned on the Up Hose in all window
return data/status packets so that the I/O port can target the requesting
commanding node with the data or status of the transaction.
Clock 1, <25:15>
Are always zero.
Clock 1, <14>
Indicates read/write: 0 is read, 1 is write. For this packet bit <14> is al-
ways zero.
Clock 1, <13:12>
Command field. The field value is 11 for all window command packets.
Clock 1, <11:4>
Are always zero.
Clock 1, <3:2>
Byte length field, LEN<1:0>. The Length field decode is specific to the tar-
geted remote I/O adapter.
Clock 1, <1:0>
SPC<1:0> field. The space field indicates which PCI address space is in
use as follows:
SPC<1:0> PCI Address Space
00
01
10
11
Dense memory space (not used with this packet)
Sparse memory space
Sparse I/O space
Sparse configuration space
Clock 2, <31:27>
Byte-aligned address for the targeted remote I/O adapter. Bits <31:27>
are always zero.
Clock 2, <26:0>
Byte-aligned address <26:0> for the targeted remote I/O adapter.