82801DB Datasheet, PDF (225/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Functional Description
Table 5-96. Read Cycle Format
Bit
Description
1 Start
2–8 Slave Address – 7 bits
9 Write
10 ACK
11–18 Command code – 8 bits
19 ACK
20 Repeated Start
21–27 Slave Address - 7 bits
28 Read
29 ACK
30–37 Data Byte
38 NOT ACK
39 Stop
Driven by:
Comment:
External Microcontroller
External Microcontroller
Must match value in Receive Slave Address
register
External Microcontroller Always 0
Intel^® ICH4
External Microcontroller
Indicates which register is being accessed.
See Table 5-97.
ICH4
External Microcontroller
External Microcontroller
Must match value in Receive Slave Address
register
External Microcontroller Always 1
ICH4
ICH4
Value depends on register being accessed.
See Table 5-97.
External Microcontroller
External Microcontroller
Table 5-97. Data Values for Slave Read Registers (Sheet 1 of 2)
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
4
0
1 = The Intruder Detect (INTRD_DET) bit is set. This indicates that the system cover has
probably been opened.
4
1
1 = BTI Temperature Event occurred. This bit will be set if the Intel^® ICH4’s THRM# input
signal is active. Need to take after polarity control.
4
2 Boot-Status. This bit will be 1 when the processor does not fetch the first instruction.
Intel^® 82801DB ICH4 Datasheet
225