Intel
82801BA ICH2 Datasheet
2-13
Signal Description
2.20.2
Test Signals
2.20.2.1
Test Mode Selection
When PWROK is active (high), driving RTCRST# low for a number of PCI clocks (33 MHz) will
activate a particular test mode as specified in
Table 2-21
.
Note:
RTCRST# may be driven low any time after PCIRST is inactive. Refer to
Chapter 17, “Testability”
for a detailed description of the ICH2 test modes.
2.20.2.2
Test Straps
The ICH2’s TP[0] (Test Point) signal must be pulled to VccSus3_3 with an external pull-up
resistor.
FS[0]
Reserved
System designers should include a placeholder for a pull-down
resistor on FS[0] but
do not populate the resistor
.
GNT[A]#
Top-Swap
Override
Rising
Edge of
PWROK
The signal has a weak internal pull-up. If the signal is sampled low,
the system is strapped to the “Top-Swap” mode (ICH2 will invert A16
for all cycles targeting FWH BIOS space). The status of this strap is
readable via the Top-Swap bit (bit 13, D31: F0, Offset D4h). Note that
software will not be able to clear the Top-Swap bit until the system is
rebooted without GNT[A]# being pulled down.
HLCOMP
Enhanced
Hub
Interface
Mode
During
PCIRST#
assertion
If this signal is sampled high (via an external pull-up to VCC1_8), the
normal hub interface buffer mode will be selected. If this signal is
sampled low (via an external pull-down), the enhanced hub interface
buffer mode will be selected.
See the specific platform design guide for resistor values and routing
guidelines for each hub interface mode.
SPKR
No
Reboot
Rising
Edge of
PWROK
The signal has a weak internal pull-up. If the signal is sampled low,
the system is strapped to the “No Reboot” mode (ICH2 will disable
the TCO Timer system reboot feature). The status of this strap is
readable via the NO_REBOOT bit (bit 1, D31: F0, Offset D4h).
Table 2-20. Functional Strap Definitions (Continued)
Signal
Usage
When
Sampled
Comment
Table 2-21. Test Mode Selection
Number of PCI Clocks RTCRST# driven low after
PWROK active
Test Mode
<4
No Test Mode Selected
4
XOR Chain 1
5
XOR Chain 2
6
XOR Chain 3
7
XOR Chain 4
8
All “Z”
9–24
Reserved. DO NOT ATTEMPT
>24
No Test Mode Selected
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