Design Guide

Platform Design Checklist
R
302 Intel
®
855GM/855GME Chipset Platform Design Guide
16.7.2. GPIO
Note: Ensure ALL unconnected signals are OUTPUTS ONLY. Only GPIO[7:0] are 5 V tolerant.
Recommendations 9
GPIO[7] & [5:0]:
• These pins are in the Main Power Well. Pull-ups must use the V
CC
3_3 plane.
• Unused core well inputs must be pulled up to V
CC
3_3.
• GPIO[1:0] can be used as REQ[B:A]#.
• GPIO[1] can be used as PCI REQ[5]#.
• GPIO[5:2] can be used as PIRQ[H:E]#.
• These signals are 5 V tolerant.
• These pins are inputs.
GPIO[8] & [13:11]:
• These pins are in the Resume Power Well. Pull-ups go to V
CC
Sus3_3 plane.
• Unused resume well inputs must be pulled up to V
CC
Sus3_3.
• These are the only GPIs that can be used as ACPI compliant wake events.
• These signals are not 5V tolerant.
• GPIO[8] can be used as SMC_EXTSMI#
• GPIO[11] can be used as SMBALERT#.
• GPIO[13] can be used as SMC_WAKE_SCI#
• These pins are inputs
GPIO[23:16]:
• Fixed as output only. Can be left NC.
• In Main Power Well (V
CC
3_3).
• GPIO[17:16] can be used as GNT[B:A]#.
• GPIO[17] can be used as PCI GNT[5]#.
• STP_PCI#/GPIO[18] – used in mobile as STP_PCI# only.
• SLP_S1#/GPIO[19] - used in mobile as SLP_S1# only.
• STP_CPU#/GPIO[20] - used in mobile as STP_CPU# only.
• C3_STAT#/GPIO[21] - used in mobile as C3_STAT# only.
• CPUPERF#/GPIO[22] - open drain signal. Used in mobile as CPUPERF# only.
• SSMUXSEL/GPIO[23] - used in mobile as SSMUXSEL only.
GPIO[28,27,25,24]:
• I/O pins. Default as outputs. Can be left as NC.
• These pins are in the Resume Power Well.
• CLKRUN#/GPIO[24] (Note: use V
CC
3_3 if signal is required to be pulled-up)
• GPIO[28, 27, 25] from resume power well (V
CC
Sus3_3). (Note: use V
CC
3_3 if this signal is
required to be pulled-up)
• These signals are NOT 5-V tolerant.
• GPIO[25] can be used as AUDIO_PWRDN.
GPIO[43:32]:
• I/O pins. From main power well (V
CC
3_3).
• Default as outputs when enabled as GPIOs.
• These signals are NOT 5-V tolerant.
• GPIO[32] can be used as AGP_SUSPEND#.
• GPIO[33] can be used as KSC_VPPEN#.
• GPIO[34] can be used as SER_EN.
• GPIO[35] can be used as FWH_WP#.
• GPIO[36] can be used as FWH_TBL#.
• GPIO[40] can be used as IDE_PATADET.
• GPIO[41] can be used as IDE_SATADET.