WM8850
Pre-Production
UNSOLICITED RESPONSE TYPES
There are three types of flags that are returned by the WM8850, prefixed in the register map as
follows:
SF = UNSOLICITED RESPONSE STATUS FLAG
Unsolicited Response Status Flags (SF) are used to indicate that there has been a change in flag
state, and (where possible) convey what the new state is. A change in state is typically something
that will persist for a number of HDA frames. A state change will trigger an Unsolicited Response, but
it is possible that a state change can occur more than once while an Unsolicited Response is being
queued.
To indicate this, Unsolicited Response Status Flags are 2-bits wide and are encoded as follows:
0h = Flag did not trigger Unsolicited Response.
1h = Rising edge of flag triggered Unsolicited Response.
2h = Falling edge of flag triggered Unsolicited Response.
3h = Rising and falling edges of the flag have been detected while the Unsolicited Response has
been queued
When the Unsolicited Response Status Flag is reported as 0h, the user is informed that there has
been no change in status. When the Unsolicited Response Status Flag is reported as 1h or 2h, the
user is informed that there has been a change in status and what the new status value is. When the
Unsolicited Response Status Flag is reported as 3h, the user is informed of a multiple change in
status, and the user should read the associated flag’s status register to get the current status value of
the flag.
UF = UNSOLICITED RESPONSE UPDATE FLAG
Unsolicited Response Update Flags (UF) are used to indicate that there has been one or more
changes to the value of some status registers. The status register should be read (through the issue
of the appropriate Get command), to see the current register value.
EF = UNSOLICITED RESPONSE EVENT FLAG
Unsolicited Response Event Flags (EF) are used to indicate that an event has occurred during an
HDA Frame. The occurrence of an event will trigger an Unsolicited Response.
PP, April 2011, Rev 3.2
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