JAJSQ97J may 2009 – january 2021 XIO2001
PRODUCTION DATA
The bridge supports the PCI Express in-band beacon feature. Beacon is driven on the upstream PCI Express link by the bridge to request the reapplication of main power when in the L2 link state. To enable the beacon feature, bit 10 (BEACON_ENABLE) in the general control register at offset D4h is asserted. See Section 8.4.66, General Control Register, for details.
If the bridge is in the L2 link state and beacon is enabled, when a secondary PCI bus device asserts PME, then the bridge outputs the beacon signal on the upstream PCI Express link. The beacon signal frequency is approximately 500 kHz ± 50% with a differential peak-to-peak amplitude of 500 mV and no de-emphasis. Once the beacon is activated, the bridge continues to send the beacon signal until main power is restored as indicated by PERST going inactive. At this time, the beacon signal is deactivated.