Ac_Sdout Pin Consideration; Siu0_Dtr# Pin Consideration; Communication Network Riser - Intel 855GME Design Manual

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Intel 855GME Chipset and Intel
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Intel 6300ESB Design Guidelines
9.4.4

AC_SDOUT Pin Consideration

AC_SDOUT is used as both the output signal to the system speaker and as a functional strap. The
strap function enables or disables the Safe Mode function based on the state of the AC_SDOUT pin
on the rising edge of PWROK. When enabled, the 6300ESB will force the appropriate bits to
engage Safe Mode. The status of this strap is readable through the SAFE_MODE bit (bit 2, D31:
F0, Offset D4h). The AC_SDOUT signal has a weak integrated pull-down resistor (the resistor is
only enabled during boot/reset). Therefore, its default state is a logical zero or set to reboot.
To disable the feature, a jumper may be populated to pull the signal line high. The value of the
pull-up must be such that the voltage divider output caused by the pull-up and the 6300ESB's
integrated pull-down resistor will be read as logic high (0.5 V
9.4.5

SIU0_DTR# Pin Consideration

SIU0_DTR# is used as both the output signal to the system speaker and as a functional strap. The
strap function enables or disables the Top Swap function based on the state of the SIU0_DTR# pin
on the rising edge of PWROK. When disabled, the 6300ESB will not invert A16 for cycles
targeting FWH BIOS space. The status of this strap is readable through the TOP_SWAP bit (bit 5,
D31: F0, Offset D5h). The SIU0_DTR# signal has a weak integrated pull-up resistor (the resistor is
only enabled during boot/reset). Therefore, its default state is a logical zero or set to reboot.
To disable the feature, a jumper may be populated to pull the signal line low. The value of the
pull-down must be such that the voltage divider output caused by the pull-down and the 6300ESB's
integrated pull-up resistor will be read as logic low.
9.5

Communication Network Riser

The Communication and Networking Riser (CNR) Specification defines a hardware scalable
Original Equipment Manufacturer (OEM) motherboard riser and interface. This interface supports
AC'97 multi-channel audio, V.90 analog modem, phone-line based networking, SMBus Interface
Power Management Rev 1.1, and USB 2.0. The CNR Specification defines the interface, which
should be configured prior to shipment of the system. Standard I/O expansion slots, such as those
supported by the PCI bus architecture, are intended to continue serving as the upgrade medium.
The CNR mechanically shares a PCI slot, therefore, the system designer will not sacrifice a PCI
slot if they decide not to include a CNR in a particular build. For more information, refer to the
Communication and Network Riser Specification, Revision 1.2 , available at
http://developer.intel.com/technology/cnr/download.htm
Figure 104
document for the corresponding design and layout guidelines. Refer to the CNR Specification for
additional information.
206
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6300ESB ICH Embedded Platform Design Guide
shows the interface for the CNR connector. Refer to the appropriate section of this
3.3 to V 3.3 + 0.5 V).
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