82801DB Datasheet, PDF (120/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Functional Description
Remote Read Message
Remote read message is used when a local APIC wishes to read the register in another local APIC.
The I/O APIC in the ICH4 neither generates or responds to this cycle. The message format is same
as short message for the first 21 cycles.
Table 5-24. Remote Read Message
Cycle
Bit 1
Bit 0
Comments
1
1
2–5
ARBID
6
NOT(DM)
7
NOT(M1)
8
NOT(L)
9
NOT(V7)
10
NOT(V5)
11
NOT(V3)
12
NOT(V1)
13
NOT(D7)
14
NOT(D5)
15
NOT(D3)
16
NOT(D1)
17
NOT(C1)
18
1
19
NOT(A)
20
NOT(A1)
21
d31
22
d29
23
d27
24
d25
25
d23
26
d21
27
d19
28
d17
29
d15
30
d13
31
d11
32
d09
33
d07
34
d05
35
d03
36
d01
37
S
38
C
39
1
0
1
NOT(M2)
NOT(M0)
NOT(TM)
NOT(V6)
NOT(V4)
NOT(V2)
NOT(V0)
NOT(D6)
NOT(D4)
NOT(D2)
NOT(D0)
NOT(C0)
1
NOT(A)
NOT(A1)
d30
d28
d26
d24
d22
d20
d18
d16
d14
d12
d10
d08
d06
d04
d02
d00
S
C
1
Normal Arbitration
Arbitration ID
DM = Destination Mode from bit 11 of the redirection table register
M2-M0 = Delivery Mode from bits 10:8 of the redirection table
register
L = Level, TM = Trigger Mode
Interrupt vector bits V7–V0 from redirection table register
Destination field from bits 63:56 of redirection table register
Checksum for Cycles 6–16
Postamble
Status Cycle 0.
Status Cycle 1.
Remote register data 31-0
Data Status: 00 = valid, 11 = invalid
Check Sum for data d31-d00
Idle
NOTE: Cycle 21 through 36 contain the remote register data. The status information in cycle 37 specifies if the
data is good or not. Remote read cycle is always successful (although the data may be valid or invalid)
in that it is never retried. The reason for this is that Remote Read is a debug feature, and a "hung"
remote APIC that is unable to respond should not cause the debugger to hang.
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Intel^® 82801DB ICH4 Datasheet