82801DB Datasheet, PDF (235/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Functional Description
5.19.2.14 Input Slot 0: Tag Phase
Input slot 0 consists of a codec ready bit (bit 15), and slot valid bits for each subsequent slot in the
frame (bits [14:3]).
The codec ready bit within slot 0 (bit 15) indicates whether the codec on the AC-link is ready for
register access (digital domain). If the codec ready bit in slot 0 is a zero, the codec is not ready for
register access. When the AC-link codec ready bit is a 1, it indicates that the AC-link and codec
control and status registers are in a fully operational state. The codec ready bits are visible through
the Global Status register of the ICH4. Software must further probe the Powerdown Control/Status
register in the codec to determine exactly which subsections, if any, are ready.
Bits [14:3] in slot 0 indicate which slots of the input stream to the ICH4 contain valid data, just as
in the output frame. The remaining bits in this slot are stuffed with zeros.
5.19.2.15 Input Slot 1: Status Address Port / Slot Request Bits
The status port is used to monitor status of codec functions including, but not limited to, mixer
settings and power management.
Slot 1 must echo the control register index, for historical reference, for the data to be returned in
slot 2, assuming that slots 1 and 2 had been tagged valid by the codec in slot 0.
For variable sample rate output, the codec examines its sample rate control registers, the state of its
FIFOs, and the incoming SDOUT tag bits at the beginning of each audio output frame to determine
which SLOTREQ bits to set active (low). SLOTREQ bits asserted during the current audio input
frame signal which output slots require data from the controller in the next audio output frame. For
fixed 48 kHz operation the SLOTREQ bits are always set active (low) and a sample is transferred
each frame.
For variable sample rate input, the tag bit for each input slot indicates whether valid data is present
or not.
Table 5-101. Input Slot 1 Bit Definitions
Bit
Description
19 Reserved (Set to zero)
18:12
11
10
Control Register Index (Stuffed with zeros if tagged invalid)
Slot 3 Request: PCM Left Channel⁽¹⁾
Slot 4 Request: PCM Right Channel⁽¹⁾
9 Slot 5 Request: Modem Line 1
8 Slot 6 Request: PCM Center Channel⁽¹⁾
7 Slot 7 Request: PCM Left Surround⁽¹⁾
6 Slot 8 Request: PCM Right Surround⁽¹⁾
5 Slot 9 Request: PCM LFE Channel⁽¹⁾
4:2 Slot Request 10–12: Not Implemented
1:0 Reserved (Stuffed with zeros)
NOTES:
1. Slot 3 Request and Slot 4 Request bits must be the same value (i.e., set or cleared in tandem). This is also
true for the Slot 7 and Slot 8 Request bits, as well as the Slot 6 and Slot 9 Request bits.
Intel^® 82801DB ICH4 Datasheet
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