Valid Codec Configurations; Usb Guidelines; Table 35. Codec Configurations - Intel Pentium 4 Design Manual

I/O Controller Hub 2
9.3.2

Valid Codec Configurations

Table 35. Codec Configurations

Valid Codec Configurations
AC(Primary)
MC(Primary)
AMC(Primary)
AC(Primary) + MC(Secondary)
AC(Primary) + AC(Secondary)
AC(Primary) + AMC(Secondary)
9.4

USB Guidelines

The following are general guidelines for the USB interface:
• Unused USB ports should be terminated with 15 kΩ pull-down resistors on both P+/P- data
lines.
• 15 Ω series resistors should be placed as close as possible to the ICH2 (<1 inch). These series
resistors are required for source termination of the reflected signal.
• Optional 47 pF capacitors must be placed as close to the ICH2 as possible and on the ICH2
side of the series resistors on the USB data lines (P0+/-, P1+/-, P2+/-, P3+/-). These
capacitors are there for signal quality (rise/fall time) and to help minimize EMI radiation.
• 15 kΩ ±5% pull-down resistors should be placed on the USB side of the series resistors on the
USB data lines (P0+/- ... P3+/-), and are REQUIRED for signal termination by USB
specification. The length of the stub should be as short as possible.
• The trace impedance for the P0+/-... P3+/- signals should be 45 Ω (to ground) for each USB
signal P+ or P-. The impedance is 90 Ω between the differential signal pairs P+ and P- to
match the 90 Ω USB twisted pair cable impedance. Note that twisted pair characteristic
impedance of 90 Ω is the series impedance of both wires, resulting in an individual wire
presenting 45-Ω impedance. The trace impedance can be controlled by carefully selecting the
line width, trace distance from power or ground planes, and physical proximity of nearby
traces.
• USB data lines must be routed as critical signals. The P+/P- signal pair must be routed
together, parallel to each other on the same layer, and not parallel with other non-USB signal
traces to minimize crosstalk. Doubling the space from the P+/P- signal pair to adjacent signal
traces will help to prevent crosstalk. Do not worry about crosstalk between the two P+/P-
signal traces. The P+/P- signal traces must also be the same length. This will minimize the
effect of common mode current on EMI. Lastly, do not route over plane splits.
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Intel Pentium 4 Processor / Intel
Invalid Codec Configurations
MC(Primary) + X(any other type of codec)
AMC(Primary) + AMC(Secondary)
AMC(Primary) + MC(Secondary)
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850 Chipset Family Platform Design Guide
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