Figure 104. Intel ® Ich2 Oscillator Circuitry; Ac '97 - Intel 815EG Design Manual

R
®
Figure 104. Intel ICH2 Oscillator Circuitry
VCC3_3SBY
Capacitors C2 and C3 are crystal dependent
14.4.13

AC '97

Checklist Items
AC_BITCLK
AC_SYNC
AC_SDOUT
AC_SDIN[1],
AC_SDIN[0]
CDC_DN_ENAB#
®
Intel 815EG Chipset Platform Design Guide
1kΩ Ω Ω Ω
1kΩ Ω Ω Ω
C1
VBAT_RTC
0.047uF
• No extra pull-down resistors required.
• When nothing is connected to the link, BIOS must set a shut off bit for the
internal keeper resistors to be enabled. At that point, you do not need pull-
ups/pull-downs on any of the link signals.
• No extra pull-down resistors required. Some implementations add termination
for signal integrity. Platform specific.
• Requires a jumper to 8.2 k Ω pull-up resistor. Should not be stuffed for default
operation.
• This pin has a weak internal pull-down. To properly detect a safe_mode
condition a strong pull-up will be required to over-ride this internal pull-down.
• Requires pads for weak 10 k Ω pull-downs. Stuff resistor for unused AC_SDIN
signal or AC_SDIN signal going to the CNR connector.
• AC_SDIN[1:0] are inputs to an internal OR gate. If a pin is left floating, the
output of the OR gate will be erroneous.
• If there is no codec on the system board, then both AC_SDIN[1:0] should be
pull-down externally with resisters to ground.
• If the primary codec is down on the motherboard, this signal must be low to
indicate the motherboard codec is active and controlling the AC '97 interface.
1.0uF
32768 Hz
Xtal
1
C2
Recommendations
System Design Checklist
2
VCCRTC
3
RTCX2
R1
10MΩ Ω Ω Ω
4
RTCX1
R2
1
C3
10MΩ Ω Ω Ω
5
VBIAS
6
VSS
185