82801DB Datasheet, PDF (55/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Signal Description
Figure 2-3. Example V5REF Sequencing Circuit
Vcc Supply
(3.3 V)
Diode
5 V Supply
1 kΩ
1 µF
To System
5VREF
To System
2.20.4 Test Signals
2.20.4.1
Test Mode Selection
When PWROK is active (high) for at least 76 PCI clocks, driving RTCRST# active (low) for a
number of PCI clocks (33 MHz) will activate a particular test mode a specified in Table 2-21.
Note: RTCRST# may be driven low any time after PCIRST is inactive. Refer to Section 19.1 for a
detailed description of the ICH4 test modes.
Table 2-21. Test Mode Selection
Number of PCI Clocks RTCRST#
Driven Low after PWROK Active
<4
4
5
6
7
8
9–13
14
15–42
43–51
52
53
>53
Test Mode
No Test Mode Selected
XOR Chain 1
XOR Chain 2
XOR Chain 3
XOR Chain 4
All “Z”
Reserved. DO NOT ATTEMPT
Long XOR
Reserved. DO NOT ATTEMPT
No Test Mode Selected
XOR Chain 6
XOR Chain 4 Bandgap
No Test Mode Selected
Intel^® 82801DB ICH4 Datasheet
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