307013-003 Datasheet, PDF (229/848 Pages) Intel Corporation – Intel I/O Controller Hub 7

Functional Description
5.21.7.2
Format of Read Command
The external master performs Byte Read commands to the ICH7 SMBus Slave I/F. The
“Command” field (bits 18:11) indicate which register is being accessed. The Data field
(bits 30:37) contain the value that should be read from that register. Table Table 5-56
shows the Read Cycle Format. Table 5-57 shows the register mapping for the data
byte.
Table 5-56. Read Cycle Format
Bit
Description
1
8:2
9
10
18:11
19
20
27:21
28
29
Start
Slave Address - 7
bits
Write
ACK
Command code - 8
bits
ACK
Repeated Start
Slave Address - 7
bits
Read
ACK
Driven by
External Microcontroller
External Microcontroller
External Microcontroller
Intel^® ICH7
External Microcontroller
ICH7
External Microcontroller
External Microcontroller
External Microcontroller
ICH7
37:30 Datay Byte
ICH7
38 NOT ACK
39 Stop
External Microcontroller
External Microcontroller
Comment
Must match value in Receive Slave
Address register
Always 0
Indicates which register is being
accessed See Table 5-57
Must match value in Receive Slave
Address register
Always 1
Value depends on register being
accessed. See Table 5-57
Table 5-57. Data Values for Slave Read Registers
Register
Bits
Description
0
7:0
Reserved
System Power State
000 = S0
001 = S1
010 = Reserved
1
2:0
011 = S3
100 = S4
101 = S5
110 = Reserved
111 = Reserved
1
7:3
Reserved
2
3:0
Frequency Strap Register
2
7:4
Reserved
3
5:0
Watchdog Timer current value
3
7:6
Reserved
Intel ^® ICH7 Family Datasheet
229