Intel 600 Series Chipset Family PCH Datasheet, Volume 1 of 2

Datasheet

ID 648364
Date 28/10/2021 00:00:00
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External CL_RST# Pin Driven/Open-drained Mode Support

The WLAN has transitioned to 1.8 V for external CL_​RST# pin, while PCH Controller Link I/O buffer still drives 3.3 V on this pin. This creates voltage in-compatibility issue. In order to support either 1.8 V or 3.3 V on the device CL_​RST# pin, the PCH operates/controls the CL_​RST# pin as dual modes, which is determined by a Soft-strap bit:

  1. Driven mode: To drive “1” on this pin, Controller Link turn-on the output enable and output=1 to drive 3.3 V on this pin. This mode can only be enabled with older version of WLAN which is 3.3 V tolerant.
  2. Open-drain mode: To drive “1”, Controller Link turn-off the output-enable, and external (required) pull-up will pull the pin up to 1.8 V, which is compatible with WLAN voltage requirement.