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M.2 connector type (key B) support PCIe ×2, SATA, USB 2.0 and 3.0, audio, UIM, HSIC, SSIC, I2C and SMBus.

I want to use SATA interface with my device, but I need to detect the reboot of the host machine (at my SATA device).

PCIe required PRST# pin (for PCIe reset). At M.2 there is a separate pin for that purpose.

My question is:
Will PRST# be toggled during the reboot of the host machine (or at the start of the host)? Even if the connected external device will be used by SATA.

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1 Answer 1

Reset to default
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I wouldn't rely on the pin ever going high in SATA mode, because keeping the reset asserted provides a cheap method of not confusing a connected PCIe card with SATA traffic.

The SATA link will go into an error state when the host resets, and a COMRESET / COMINIT is required to come out of it.

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  • \$\begingroup\$ do you see any other ways except to work with COMMRESET/COMMINIT commands at SATA? Actually, I will have no way to control (react at) the commands at SATA. I will have an bridge from SATA to eMMC and will have an control a flow at eMMC side. \$\endgroup\$ Commented Oct 28, 2021 at 15:38
  • \$\begingroup\$ None that work reliably, but the bridge might reset itself on loss of communication and forward this to the eMMC. \$\endgroup\$ Commented Oct 29, 2021 at 8:56

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