9.5.2 WLAN IRQ Operation (SDIO Out-of-Band Interrupt)

The WLAN IRQ is an out-of-band interrupt request line that is not defined by the SDIO standard specification. Therefore, a good understanding on how it works is required in order to work with the WL8xx solution.

The WLAN_IRQ line operates as follows:

• The default state of the WLAN_IRQ prior to device enable is internal 100K pulldown (in case of a debug mode there is external 10K pull up)
• After the enable line is applied high, the WL_IRQ is changed to drive logic '0'.
• During firmware initialization, the WLAN_IRQ is configured by the SDIO module.
  • The WLAN firmware creates an interrupt-to-host request, indicated by a 0-to-1 transition on the WLAN_IRQ line (the host must be configured as active high or rising-edge detect).
  • After the host is available, depending on the interrupt priority and other host tasks, it masks the firmware interrupt. The WLAN_IRQ line returns to 0 (a 1-to-0 transition on the WLAN_IRQ line).
  • The host reads the internal register status to determine the interrupt sources. The register is cleared after the read.
  • The host processes all the interrupts read from this register in sequence.
  • The host unmasks the firmware interrupts.
• The host is ready to receive another interrupt from the WLAN device.

Figure 7. WLAN_IRQ Signal on System Wake Up

For more details on the Wake on Wlan feature, see ^[3].